How to run a Macro in Excel only in a certain column?

This macro for excel automatically links all checkboxes in my active worksheet to the cell they are in. However I need it to run only in a certain column and not the whole worksheet. The code looks as follows:

Dim chk As CheckBox

For Each chk In ActiveSheet.CheckBoxes
    chk.LinkedCell = chk.TopLeftCell.Offset(0, 0).Address
Next

End Sub