You can actually add the two expressions into one, just take care of the null values. if you dimension is time though, you could end with a gap. For example, if expr1 is up to 2012P11, and exp2 for 2012P12 and over, there will be a gap in the line.
If you could give more details, I could be of better help.
Se euxaristw gianni gia ton xrono sou kai thn bohtheia sou.
What i actually have is a Quantities comparison graph by time. Where i have 3 plot lines one for Actual Quant,one for Forecast Quant and one for Budget Quant. The data will contain no null values so there is no consistency problem.
How can I manage to fit two expressions in one as you said i have not figured it out. I have sum(Actual.Quant) and
sum(Budget.Quant) as my expressions.