High-balance reporting?

[Matthew Pounsett]

I've been poking around in GnuCash trying to find a way to report on the
high balance for a list of accounts in a given period.  This would be
hugely helpful in FBAR reporting (Foreign Bank and Financial Accounting
Report) for the IRS.

I imagine I'm going to need to look into writing custom reports, but before
I dug into that I thought I'd ask if anyone else has already solved the
problem.