procedure MouseMove(Shift: TShiftState; X, Y: Integer); override;
DYNAMIC void __fastcall MouseMove(System::Classes::TShiftState Shift, int X, int Y);
Provides visual feedback of how the neighboring control would be resized.
After calling the inherited method, MouseMove computes the new boundaries of the neighboring control and draws a line where the new edge would be. The control is not actually resized until the mouse is released.