Indesign CS5 Conditional Data Merges

So the request has been made by another department to merge data conditionally: if X is not null, then populate Y.

We're a bunch of graphic designers using Indesign CS5, and while we're pretty comfortable with Indesign's data merging, I think we may have discovered its limitations.

I've found a couple of products, such as DesignMerge that say they can do conditional data merges. But it costs between $1,000 - $3,000 dollars!

Anybody ever do conditional data merges in Indesign? Got any hints for us?

Hopefully one that doesn't cost $1,000?

Thanks!