Your process is a bit vague but presumably you will get the office (here a string strOffice) from the userform, so something along the lines of:
Code:
Dim oDoc As Document
Dim strOffice As String
Select Case strOffice
Case "London"
Set oDoc = Documents.Add("c:\path\London templatename.dotm")
Case "New York"
Set oDoc = Documents.Add("c:\path\NY templatename.dotm")
'etc
End Select
'do stuff with oDoc