"DRKENNE" wrote:
I'm looking for a formula (simple I hope) that would calculate interest
that's been accruing at an annual rate of 10% on $10,500 that should have
been paid on 3/6/07 and no payment has been made. Since there is no end date
at this time, I'd be using the date (today) of the calculation.

So many details are missing. I don't see how anyone can offer you a
formula, much less a simple one, unless they get lucky in their
ass-u-me-tions.

For starters, does interest compound? If so, what's the compounding
frequency?

You say that interest "has been accruing" on $10,500. When did interest
start accruing?

Finally, what type of investment is this? That might help in providing the
"simplest" solution.

You might take a look at the ACCRINT and ACCRINTM functions. But if you use
them blindly, their results might not be relevant. GIGO.