How do I add a User Defined Function to Excel? - vba

Question

I have a simple stored procedure that returns a Description and a Name when you give it a ID. I need to enable this inline in multiple Excel Sheets. Something like =ItemLookup('12345') that would then return the aforementioned info.
I have not done a lot with Excel programming and am simply wondering what my options are for tackling this. Is this a VBA thing or should this be an external DLL that I COM register? Both felt like overkill but then I realized I had no idea if they were. I really wanted to use VSTO for this but it sounds like that is not possible for Cell level UDF's without having to modifiy each Workbook with some VBA.

Answer 1

The best way to add UDF functions to Excel is with Excel-DNA (which is a free, open-source library I develop), and any of the .NET languages - VB.NET, C# and F# are all fine.
To get started you make a new 'Class Library' project in Visual Studio (any edition), install the 'Excel-DNA' package from the NuGet package manager, and add your code:
Public Module MyDataAccessFunctions
<ExcelFunction(Description:="Gets the Item from the database")>
Public Function ItemLookup(code As String) As String
' Here you have to do some work to get the data
Return "Hello " & code
End Function
End Module
Pressing F5 builds and starts Excel, and you're done - try putting =ItemLookup("Paladin") into a cell.
The resulting add-in is a single .xll file, which you can copy and use on any machine that has .NET without any installation or admin permissions. It works with old Excel versions too.
The best place for support (including absolute beginners' questions) is the Excel-DNA Google group.

Answer 2

You can use Excel to create a VBA UDF pretty easily, just hit alt+f8, right click your project in the project hierarchy on the left of the screen, and click add module.
Here is a quick Hello World function you can just paste into the module, then click play (or alt+f8 from worksheets)
sub test()
msgbox "helloworld"
end sub
If it was me, I would probably just create a list of the file paths that need to be searched. Then create a VBA macro that opens them in excel, searches them for the key, and returns other information from the row the key was found on.
You can open files with the 'Application.Open' method, simply pass in
the file path as an argument. 'Application.Open' returns a workbook
object.
Each workbook will have several worksheets, you can access them
through the workbook's 'Worksheet' property
Getting each used cell in a workbook can be done via looping through the 'UsedRange'
property in each worksheet
Get the value of a cell for comparison from the cell's 'value' property
Cells also have a 'row' property so you can find other items on the same row
If you're used to VBA you could get this running in less than an hour. But since you're just starting out it'll probably take a 3+ hours since you'll have more research/debugging