I could use some help on understanding BINDEVENT

I have a grid with 30 columns or so. I would like the VALID event for each text box to call a form method. In the form Init I have

WITH myGrid
    FOR I = 1 TO 30
        oCol = EVAL("column"+TRANSFORM(I))
        oCol.controlsource = "something"
        BINDEVENT(ocol.text1,"valid",thisform,"calc_bld_qty")
    ENDFOR
ENDWITH

For the moment CALC_BLD_QTY is just a Messagebox.

If I put a value in the cell and press ENTER/ARROW/TAB etc nothing happens.

If I put something in the Valid code for the TextBox (for example another Messagebox), then CALC_BLD_QTY fires and then the other Messagebox fires.

What have I missed in the proper way to set this up?

Thanks to all..........Rich