Expects: AX    0008H
CX    minimum Y coordinate (vertical pixel position)
DX    maximum Y coordinate (vertical pixel position)
                                                                  
Returns: none
                                                                  
Info: This sets a vertical range out of which the mouse pointer will
not be able to move.  Attempts by the user (or the program via
INT 33H 0004H) to move above CX or below DX will cause the
pointer to remain at the minimum or maximum value in the range.

Use INT 33H 0007H to limit motion on the horizontal axis.

Notes: All X,Y coordinates are virtual coordinates and when working with
text mode, you must divide each value by 8 to get a character
clm,row.

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INT 33H 0008H: Set Vertical Range