This may be too round-about, and I'm not sure if it will be feasible for
your true data set, but maybe it can give an idea.
I have two mock datasources: cost and revenue.
(I didn't quite catch how they were different with respect to granularity.
Please revise them as needed to match yours, and repost.)
To each datasource, I added a Lookup sheet that contained all possible months.
I then cross-joined to this lookup sheet on a calculated field of 1 using:
So when I blended the sources, it was on word and the LookupDate,
which they both had in common. And revenue showed up in February
for Word1 even though there was no cost for that month.
The revenue and cost shown were of the form:
IF [Date]=[Lookup Date] THEN [Cost] END
Please see the workbook attached in the Forum thread.