I am creating a parametric part that has a linear rail bolted to it.  The rails come in 2mm increments.  I have the length of the Rail Pocket ("RAIL POCKET@Sketch12") and I want to round down to the closest even number.  For instance, if the pocket is 84.912mm, I want it to round down to 84mm.  To do this, I am using the following equation:

RAIL LENGTH = (INT("RAIL POCKET@Sketch12"/2)*2 

84.912mm/2 = 42.456mm

INT(42.456mm) = 42mm

42mm*2 = 84

Success!

The problem is that, when I change the document units from MMGS to IPS,  the variable "RAIL POCKET@Sketch12" is now in inches and calculates incorrectly.  

RAIL LENGTH = (INT("RAIL POCKET@Sketch12"/2)*2

3.343in/2 = 1.672in

INT(1.672in) = 1in

1in*2 = 2in

2in = 50.8mm - wrong answer

When I add numerical values to an equation that I need to be computed in a specific unit, I simply add the units after the number.  I, however, can't figure out how to do this for variables such as "RAIL POCKET@Sketch12".  I was hopeful that checking 'Override Units' in the "RAIL POCKET@Sketch12" dimension property manager and setting it to 'Millimeters' would do it but it is still calculating in inches when in IPS.

Is there anyway to force a dimension variable like "RAIL POCKET@Sketch12" to be used only in mm units for a calculation regardless of what the document units are set to?