control position vs mouse position

[dino_schraeyen]

I want to create a tooltiptext for example. I have the mouse postion, the buttonposition and the window-position. So if I'm moving the mouse-cursor over the button, a light needs to go on. To find the position of the button in function of the X-axis is no problem, but from the top I can't find. My conclusion --> The "top button position" is not right.

[Al_S]

You didn't include handy\mouse.vi, so we can't see how you're reading the mouse position. Functions that read the mouse position often report it relative to the current window. You then need to add the window position to it.
FYI: Tooltips are included in LabView 6.x. Instead of just being able to set the description of a control, on the same screen you can set the tooltip text. Just one minor reason of many reasons to upgrade.