re access 2007

i have a form A that has been made the parent of form B by a call to the win api function SetParent (don't ask) ; here is roughly what they look like together:

AAAAAAAAAAAAAAAAAAAAAAAA
AABBBBBBBBBBAAAAAAAAAAAAA
AABBBBBBBBBBAAAAAAAAAAAAA
AABBBBBBBBBBAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAA

when the right edge of A is resized, B is not resized or moved and no portion of B is hidden/covered by the borders of A, but there is a lot of flashing in the controls of B because when A is resized its background is redrawn ; i want to eliminate the flashing ; i am subclassing A, "dumping" the WM_ERASEBKGND message, intercepting A's WM_PAINT and WM_NCPAINT messages and, before passing them on to A's native winproc, validating that portion of A that is occupied by B (win api function ValidateRect), but that didn't fix the flashing ; i've tried also subclassing B and dumping its WM_ERASEBKGND, WM_PAINT and WM_NCPAINT messages, but that didn't fix the flashing



can anyone shed light on this ?