Incremental move of work offset

I have been teaching folks how to "fix" a job that isn't cutting all the way through by telling them to G0 Z6 to get to a round number, then switch the radio button in AXIS to X and hit "Touch Off" and type in 6.05 to shift the work offset to make it run the job down by 0.05" which has consistently been a good adjustment. I have to challenge them to work out which direction to move it, half instinctively think to Touch Off to 5.95 instead.  

It would actually be REALLY nice to add a button to just shift the Z offset by 0.05" in order to cut 0.05" deeper automatically.  I have a Macro button on the XHC free to do this, and/or I could add a panel button on AXIS.  

But how to do this?  Ideally, this should not involve a physical move, although that's not deal-breaker.  G10 L2 P1 Z? sets the work offset, but by an absolute value.  Can I fetch the current offset from #parameter space and add to it?

 

I solved that with pyvcp. The gcode behind is simple, and can be used from mdi, just replace 
#<FINE_CORR> with correction value. #5420-#5423 are positions in active coordinate system and #5220 is the current active coordinate system.