Procedure ScreenToVScreen(Var X1,Y1:Integer)

    Updates VX and VY       : No
    Updates Cursor Position : No

    This converts screen coordinates to window coordinates.

    For example, if the viewable  area  (screen) is from (5,5) to (84,29)
    then calling

    X:=1;
    Y:=2;
    ScreenToVScreen(X,Y);

    will cause

    X = 5  and
    Y = 6.