For populating two or more columns I generally use a two stage thing.
First AddItem to set  up the row  and then Add stuff to each column.

An actual example....

Me.lstStringSetWidth.AddItem
Me.lstStringSetWidth.List(Me.lstStringSetWidth.ListCount - 1, 0) = "Inches"
Me.lstStringSetWidth.List(Me.lstStringSetWidth.ListCount - 1, 1) = "/1000"

You can see that column  reference change from (n, 0) to (n, 1).
Using ListCount means I reference the last line... Which I've just added.