NEWERA - screen re-display

I have a small main window that only contains drop down menus. All other windows in the project are opened from this main window. Code for opening windows first checks to see if window is open then opens it and gives focus to field on window. This works fine because if a window gets hidden then it can be brought to front by clicking the menu item. Unfortunately if there are more than about 3 windows open, the refreshing only partially works and as the window comes to the front part of it is shown and part is cleared. Any suggestions? -- Mike Ripley