Calculating an APR without all variables

Interesting forum and probably my last hope of success.

I have until 2pm UK time tomorrow to complete a project that hinges on the following:-

I need to calculate the APR on 15,000 loans using Excel where the following data only exists:-

Column A: Original Amount Advanced

Column B: Term (Months)

Column C: Total Repayment

For example,

Original Amount Advanced: 10,000

Term(Months) 120 (i.e. 10 years)

Total Repayment: 14,000

In Excel Column D, I'd like to calculate the APR.

I have tried an Excel forum and its too advanced even for the "Guru's" who said it cannot be done without splitting out payments etc. I've taken a look at the APR calculation on the OFT (UK Office of fair trading) website and it's way too advanced for my primitive brain.

Can someone provide some form of solution for me? I'm still in my probation period at work and I'm really desperate for a result on this. Thank you in advance.