Compound interest on o/s invoices

[Staple]

We have a few invoices that are outstanding for 2/3 years, on which. I want to calculate the compound interest accruing to date.
The interest would be variable in line with bank overdraft rates.
Can this be done through excel or is there a formula that can be used.
Any help please.

 

[BlueSpud]

Multiplyer is

( X * ((100 + Y) / 100) to the power of Z)

where
X = original number
Y = interest rate in %
Z = no of years

e.g. X = 500, Y = 5, Z = 3

==> 500 * ((100 + 5)/ 100)ttpo 3)
= 500 * ((1.05)ttpo 3)
= 500 * 1.157625
= 578.8125

 

[Staple]

Thanks Blue Spud