(Service Call &C2000)

On entry: 
R1 =  &C2000 (reason code)
R2 =  New X position of mouse
R3 =  New Y position of mouse
R4 =  Wheel change (signed integer)
On exit:
R1 =  0 to claim, else preserved to pass on
Use: This is issued as soon as RISC-OS reaches a point where it executes its transient callbacks (ie; in SVC mode usually) after the interrupt notifying the MouseSync module of a change in mouse pointer position or wheel position.

It was intended to use this service call to implement your own mouse driver or wheel motion translator. To override the default action of setting the position of the mouse using OS_Word, claim the service call.