Is it possible to insert variable names into similar textbox names?

[salvelinus]

I'd add the third parameter (in red) below, then you can put in whatever value you want.

public sub Breakdown(byref frmToDo as form, byval strControl as string, byval strValue as string)

'---- requires 
'----    the form to look at
'----    the controls to update

'---- Call like:
'----    Breakdown me,"Vendor1", "0"

    frm.controls("TextBox" & strControl & "ImpInst").text = strValue
    frm.controls("TextBox" & strControl & "ImpWir").text = strValue
'etc.

end sub