Resizing the whole Desktop


Can anybody tell me how to resize the whole desktop with the windows
startbar. I need this to draw a border around the wohle screen for example.

Ive already tried this with the function
SystemParametersInfo(SPI_SetWorkArea, 0, pointer(@NewScreenRect),
This seems to go in the right direction but cant be all, because the
startbar doesnt resize and messageboxes dont pop up in the new middle of
the screen.

Help would be grately apreciated ...