_twM26( nB, nC, nD )
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     Set the mouse sensitivity and double speed threshold, The
     sensitivity numbers range from 0 to 100 where 50 is the default
     value in all cases. The sensitivity determines the mouse to cursor
     movement ratio with the scaling factor passed.

       Arguments:

     nB - 'N' Horizontal mickey sensitivity number.

     nC - 'N' Vertical mickey sensitivity number.

     nD - 'N' Threshold for double speed.

       Return:

     Nothing.

       Example:

     To increase sensitivity and double speed threshold by 50%:

     _twM26( 75, 75, 75 )