I'll assume you need to know how to exchange the default text object in the grid column for a combo box.
1) Select the Properties Sheet and pull down the combo box of object names. Select the first text object under the first grid column.
2) Click on the title bar of the Form Designer. Press the delete key. Poof!! There goes the text object.
3) Select a combo box control from your control toolbar and drop it in the row and column where you deleted the text object.
4) Lather, rinse, and Repeat.

>I need a Grid with table lookup in column 1 (pick
>a construction trade doing the work), table lookup
>in column 2 (what is their labor rate), input in
>column 3 (manhours), and a calc in column 4
3