First off, don't use the word "static" to do with anything C# related - it has a very specific meaning which is nothing to do with your problem! :laugh:
The problem is probably to do with the size of the user control, and how you have the Anchor and Dock properties set for the controls that make it up.
Assuming the thumbs should be to the left and right of a central trackbar, then none of them should have Dock set to anything, and the Anchor properties should be set as shown below:
thumbLeft trackBar thumbRight
Top+Left Top+Left+Right Top+Right
That way, the buttons will remain fixed size, but the right one will move relative to the right edge of the control, and the track bar will resize itself to fit.