I now managed it, to use the DrawString in the ForeLayer. (see picture in attachment)
The (blue number) 864 in Top Middle is written with DrawString over a bitmap, and both, the number and the bitmapline becomes updated every second with new data in height over ground (in meters).
For the sake of completeness, I would like to know, wether it's possible to see the line behind the text, using a imageButton, as well.
I couldn't find it out till now.
If I put the ImageButton (with transparenty checked) on the form, where the bitmap will be, and run the progi, the background of the Button is black (correct as bitmapBackground) but the(yellow) line drawn in the bitmap is masked out from the Buttons outline.
If you are drawing in forelayer all objects are drawn over, like if we had a tranparent sheet were we drew... all controls are bound to the forms layer and therefore have the forms backgroung, as it happend in your attemp to use an imagebutton...
So I would suggest that you drew all grafical inputs in forelayer and all the info bits in the forms layer, that should do what you want to achieve...