Spectre Save Statement and Functions Help?

Hello,

I am saving the vds and vdsat parameters of nmos and pmos devices during a dc sweep of temperature using the spectre save statement in IC6.1.4 for a 32nm SOI process.  By plotting these I can easily see if the device is in saturation.  What I am running into for the first time in a project is that for the pmos devices, the vdsat values are positive and the vds values are negative.  This makes comparing the signals very difficult.  I can always use the calculator to negate one, however, this is very inconvenient to do for each device. 

Is there a way to negate one of these signals in the save statement or save.scs file for easy plotting of these parameters?

Thanks in advance!