Let User Specify Excel Column To Import

I have a function within a class that imports an Excel sheet into an arraylist. I have overcome the problem of asking the user if there is a header or not. Now I want to ask the user which column is the data in. Here is my basic code for getting the header Yes/No and this is handled with a simple MessageBox... but of course this cannot be used to return a numeric value such as (0) being column #1. So I'm thinking I need a special form to pop up which the user will enter the the column being 1,2,3,4,5... etc. Of course subtracting "one" 1-1=0 is column 1 and 2-1=1 is column 2, etc.

Here's how I handled the header issue with a message box:
Private Sub ValidateCriteria()
If m_header = "" Then
GetHeader()
If m_header = "" Then Throw New Exception("Do you want to specify header row before importing?")
End If
[Code] .....