Account formula

We open new company in Uganda we lending money to people with high risk so the interess is high 20% per month less 5% commission for runners.
Some guys help us with XL as program but our self we are not good with XL.
Is there any possibility to put some formula in our PC or laptop with just a press of keyboard we know what going on.
If we can talk verbally it will be nice I can explain much better.
I really hold to you and hopefully you can help us.
Regards.

Benson Levy