INT 33 - MS MOUSE - DEFINE TEXT CURSOR

         AX = 000Ah

         BX = hardware/software text cursor

             0 software

                 CX = screen mask

                 DX = cursor mask

             1 hardware

                 CX = start scan line

                 DX = end scan line

 Note: when the software cursor is selected, the char/attribute data at the
       current screen position is ANDed with the screen mask and the
       with the cursor mask

 -----------------------------------------------------------