Control don't refresh

Hi,

I'm using some combobox amd listbox controls on one sheet of my workbook.
These controls are refreshed from several sources (other sheets, other
workbooks.) They work fine. The problem is when I refresh them I can't use

Application.ScreenUpdating = No

(macro tasks to update controls)

Application.ScreenUpdating = Yes

as I do when I'm performing other tasks on sheets. If I turn off screen
updating the controls won't refresh. They remain empty, or in some cases
they become "transparent" and I can see sheet gridlines through them when I
turn screen updating on.

For now I'm not using Application.ScreenUpdating and everything works fine
(other than the screen flashing.) Is there a workaround for this problem?

Regards,
Charlie

P.S.
Global Const Yes As Boolean = True
Global Const No As Boolean = False