Finding a previous value based on another column

[JL0101]

I have the following measure below, however it just returns blank when I insert the measure into a prexisting table, any idea why?

Model	A-Weight Difference1
a
b
c
d
e

A-Weight Difference1 =

VAR PreviousRev =

    CALCULATE ( MAX ( 'Full_Rebar'[C-Revision Number] )-1)

RETURN

    CALCULATE ( MAX ( 'Full_Rebar'[weight_calculated ), 'Full_Rebar'[C-Revision Number] = PreviousRev )

would it have anything todo with filter context? as there is another measure in the table too.

[PhilipTreacy]

@JL0101 

Please provide data and excpected result.  I can't tell from what you have provided what data you are using or what you expect is the correct result.

Regards

Phil