Lear 35A airspeed gauge

I'm trying to correct the behavior of a Lear A/S gauge. The gauge is unique in that it has a second, rotating dial that shows the Mach number. Therefore, the gauge needle points to both a "Knots" value and a "Mach" value. As downloaded, the Mach dial never changes. I want the dial to rotate with increasing altitude to reflect the fact that Mach number decreases relative to an indicated "Knots" value.The Mach dial is a masked element (a "sprite" element). I know I want the <Rotate> value to be: (A:Indicated Altitude, feet) 1000 /. And I have calculated the starting and ending values and linearity for Mach values versus altitude, but I can't get the dial to respond during a climb.What am I missing? Specifically, can a masked element--or "sprite"--be controlled like a needle element? Meaning does it respond to a "Points to" entry and X,Y values? Or must rotation be specified in degrees? Must a "Degrees Point to = -1" be used?I'd appreciate any insight!Regards,Cam