i have 12,000 records in a list box and i want to select/deselect it all. my code goes like this:

(IN COMMAND BUTTON - Click Event)

Thisform.LockScreen = .T.
FOR nloop = 1 TO Thisform.List1.ListCount
Thisform.List1.Selected(nloop) = ! Thisform.List1.Selected(nloop)
ENDFOR
Thisform.LockScreen = .F.

this works very slow, is there any solution?
Thanks in advance...