Function help

Wasup...

So i need help on making so my script won't continue to the next step until it finds my bitmap. Like the script would open a window, and when the window opens i want it to select the bitmap (i already know that so don't post about it pls), however i don't want to just plainly put in a standard wait time like 5 seconds or so, because it might not be the same on a different computer.

Basically after the procedure to open the window executes, i want it to wait until it finds that certain bitmap before it does the next steps.

Thanks