>Unfortunately ActiveX remains opaque and resizing possible without limitation only in one direction. In the direction of ActiveX it only possible in small increments ( till part of the bar is visible ).
>
> <--- okay
> editbox | activex rectangle
>
> ---> problem
> editbox | activex rectangle
>
>Any ideas ?

How about making the AX invisible while the splitter is dragged? It shouldn't hurt as you already have the lockscreen set. BTW, thisform.lockscreen, or _screen.lockscreen? IMO, you could try one at a time, and see if it changes the behavior.