Using VBA how do I return the column number of first column in a user inputted range?

Hello,

I'm creating a macro that creates a co-ocurrence matrix from variables that are adjacent to each other.

In order to proceed, I need to know how to return the column number of the first (leftmost) column in a range that the user selects.

How I obtain the range:

Dim HeaderRange As Range
'Prompt for Header Range
    Set HeaderRange = Application.InputBox(prompt:="Select the header row (These will be used to generate and label the matrix)", Type:=8)

Any help or direction would be appreciated. Questions are more than welcome, often times my posts are unclear.

Thanks!