Sony, Veda, the wording of your questions is very confusing. I'm really not sure what it is you're looking for.
It sounds like you want your program forms to resize themselves, whenever the taskbar is resized (so that the taskbar will never be hidden at all). Is that correct?
As Glenn said, if your form is Maximised, then it will resize automatically if the taskbar changes (set form.WindowState to vbMaximised).
However, if you want the same thing to happen when your forms are NOT maximised, then there is an easy solution:
1. Add a SysInfo control to your form
2. Put code in the appropriate SysInfo event (SettingChanged event, I think)
3. If the Item that changed was the Taskbar (Item=47?), then use the WorkAreaTop, WorkAreaHeight etc properties of the SysInfo control to resize/move your form.
When moving or resizing, be sure to use the WorkAreaTop and WorkAreaLeft properties, not just the WorkAreaHeight and WorkAreaWidth - they might not be zero!
In other words, DON'T assume that the Taskbar is always at the bottom of the screen. It could be at the top, left or right of the screen. I always put my taskbar at the top of the screen, because I find it vastly more ergonomic than at the bottom - and it really annoys me when programmers don't consider this, or handle it correctly.