Int 33 Fn 0019  - MS Mouse V6.0+ - Return User Alternate Interrupt Vector  [M]

   AX = 0019h
   CX = call mask (see AX=0018h)

Return: BX:DX = user interrupt vector
   CX = call mask (0000h if not found)

Note:  attempts to find a user event handler (defined by function 18h)
     whose call mask matches CX

See Also: AX=0018h