Office Add-in Development: VSTO for Excel, Word and Outlook

Which Office programs I build add-ins for

All of them are VSTO add-ins for the installed Microsoft Office on Windows. Which one is yours and how much work it carries becomes clear after the specification.

What the add-in can talk to

This is a list of what I can build, not a list of options to tick. What your add-in actually does is settled in the specification — every connection is priced by the work it carries.

• Other people's APIs and services. The add-in sends and retrieves data from your ERP, your CRM or any service with an API: signing in, sending a document, checking a status, fetching a code list. This is how the integrations with productive.io and Dropbox came about.
• Databases. Reading and writing straight from Office, over an existing database on the local network or on a server. If the database itself is the problem, that is separate work and is handled separately.
• Files and folders. Saving to an agreed location by a naming rule, reading incoming files, processing a whole folder at once, exporting into the format the other side requires.
• SharePoint and shared libraries. The document is filed from Office into the place where the company already keeps its documentation, with the fields filled in, instead of being dragged there by hand.
• Email. Advanced filtering, categories and rules that Outlook cannot do on its own, automatic replies on a condition, extracting data from a message and writing it into another system.

Why an add-in costs less than custom software

Every installed program carries a layer of work that has nothing to do with your logic: the installer, the code signing, the ribbon with its buttons and panels, error reporting, and the mechanism that offers a new version on start-up. With custom software that layer is built again and paid for.

Not with an Office add-in. That part already exists and is called Veseteo — my foundation for VSTO add-ins, on which the whole list of work below was built. You pay only for what is yours: the actions, the panels, the connections to your data and the rules the work follows.

The name Veseteo remains only as the signature of the foundation. The ribbon tab, the icons and the command names carry your name and your vocabulary, because that is what your people look at every day.

Delivered work

This is not an announcement but the largest part of my portfolio. The full list is among the Office add-in references, and here it is by program:

• Outlook
  1. Outlook talking to an external service — add-ins with API integration: contact updates and a REST API call right after a message is sent, archiving incoming mail to PDF straight into a business system, fetching and processing files from Dropbox with delivery to SharePoint, and turning email into tasks on Productive.io.
  2. Outlook putting itself in order — add-ins without an external service: email categorisation in a shared mailbox, saving attachments to an agreed location by a naming rule, automatic buffers between meetings in the calendar, and an alert with a countdown before a meeting ends.
• Word
  1. Word putting itself in order — add-ins that work on the document by rules: resizing and aligning all images in a report, a reminder to save the work where autosave does not run, and entering and printing twelve-digit numbers from a form.
  2. Enhancing Word documents with the ChatGPT OpenAI API
• PowerPoint
  1. A PowerPoint add-in that lets users replace images
• Excel
  1. Automating web interactions with a VSTO add-in in VB.Net and Selenium

Prices

An add-in for Excel, Outlook or Word starts at $198, while custom desktop software starts at 90.000 RSD. The difference is not in the amount of work on your logic but in the fact that the infrastructure is not rebuilt. The figure is a lower bound, because the scope depends on the number of actions, integrations and exceptions — the exact price and deadline come after the specification. See also what is not included.

First step

The specification is paid for and ordered first. What it covers and why we start with it.

Smaller changes to an add-in that already runs do not have to go through the whole procedure: for those there is hourly work, where you pay for the time spent. The full price list is on the pricing page.

First step: specification and estimate

I do not give a fixed price for an add-in that exists only in the sentence „we need a button in Outlook that sorts this out". So we start with a specification: a fixed price and a written document that stays with you whether or not we continue.

For an Office add-in the document answers five things:

• What the add-in does. A list of commands and panels, written in sentences the person who will use them understands, not only the programmer.
• What it talks to. A database, someone else's API, a folder, SharePoint, a mailbox — every connection separately, because that is usually where most of the work hides.
• Where it is installed. The number of computers, Office versions, 32 or 64 bit, whether a terminal session is involved, who has the right to install.
• Phases and estimate. What goes into the first delivery and what can come later, with a time estimate for each phase.
• What is not worth doing. If part of the job is solved by an existing Office option or a single rule, that is what it will say.

The specification is a separate item with its own price and is ordered straight away, because its scope and deadline are known in advance:

This amount is deducted from the price of the work if we continue. If we do not, the document stays with you and you can take it to any contractor.

What I commit to

What the price does not cover

I write this so you understand the price before ordering, not after. Everything on the list I can do, but it is agreed and charged separately.

What to prepare before we start

What this is not

So that you do not pay for a specification for work that has its own page and its own price.

Frequently asked questions