Question

I need to create a button on the worksheet, that will call function in my VSTO add-in. How I can achieve this?

Answer 1

Check out this helpful link:
http://vbadud.blogspot.com/2008/11/call-method-in-vsto-addin-from-visual.html

As it says, you need to make sure you have exposed it for external use. Once it is, the call from excel would look something like this:

Sub Execute_VSTO_Addin_Macro()

Dim oAddin As COMAddIn
Dim oCOMFuncs As Object

Set oAddin = Application.COMAddIns("CallVSTOExample")
Set oCOMFuncs = oAddin.Object

oCOMFuncs.SayHello

End Sub