expression.Column
expression Required. An expression that returns one of the objects in the Applies To list.
Example
This example sets the font to bold in every other column of the visible range on the active worksheet.
Sub BoldColumns()
Dim col
For Each col In Spreadsheet1.ActiveSheet.VisibleRange.Columns
If col.Column Mod 2 = 0 Then col.Font.Bold = True
Next
End Sub