Although you can set the opacity of many controls, the grid control will not allow this because columns in grids don't have an opacity setting.
As a test, create a form with a grid, a text box, add a table to the form's dataenvironment, and set the form's picture property to a known image file.
Set the opacity of the textbox (backstyle=0) and place the following code in the init() method of the form:
WITH THIS.grid1
FOR i = 1 TO .COLUMNCOUNT
.COLUMNS(i).text1.BACKSTYLE = 0
NEXT
ENDWITH
You'll notice the picture shows through the textbox but not the grid control.
In addition, you'll notice that the backcolor of the textbox shows when the textbox receives the focus and reverts back to underlying form's picture when it looses the focus.
As Mike states, I believe you'll need an ActiveX grid control.
Darrell