INT 33H 0019H: Query User Alternate Event Handler

 Expects: AX    0019H
          CX    event mask of desired handler (as used in INT 33H 0018H)
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 Returns: CX    event mask of handler or...
                0000H = no handler matches
          ES:DX address of matching event handler
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    Info: Use this function to obtain the address and mask of an alternate
          event handler installed via INT 33H 0018H (which see for the bit
          values for CX).

See Also: INT 33H: Mouse Support
          Interrupts and BIOS Services
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