I used a free table opened with an alias as the grids recordsource. I did all the connecting in the same form.method. The valid fired as you assumed it would. I kept all other code the same. Just the recordsource for the grid & the controlsources for the columns were changed. Here is how I create the cursor that I am trying to use. Perhaps it's here that the problen occurs

* Clear the grid
WITH THISFORM.grdpayroll
.RECORDSOURCE = ""
.SETALL("CONTROLSOURCE", "", "COLUMN")
.COLUMNCOUNT = -1
ENDWITH

SELECT * FROM gebopay WHERE gebopay.semaine = m.week_act INTO CURSOR new_cursor

* This is a check to see if the ALIAS name is in use
IF USED('main_cursor') && If so, select and close it
SELECT main_cursor
USE
ENDIF
* Transfer the newly created cursor into a ALTERABLE cursor
USE DBF('new_cursor') AGAIN ALIAS main_cursor SHARED IN 0
SELECT main_cursor

After this I call the method to attach it the grid