I don't know of any function that does that although it will propbaly exist.
But you can create the calculation step by step ( if it's a one-time task ):

Assuming that the disbursement is at the beginning of the month do this:

In A1 : enter your initial amount
In A2 : = E1
In B1 and B2: enter your monthly disbursement
In C1 : = A1 - B1
Copy C1 to C2
In D1 and D2 : Enter the growth % per month ( e.g. 0,5%)
In E1: = C1*(1+D1)
Copy E1 to E2
Now copy row 2 down until A1 becomes 0 or less.

Not very sophisticated but does the trick.

Hans


"SilkCityFlorida" wrote:

What function do I use?

I have an amount of money that will grow at a steady rate, and from which
there will be monthly disbursals of a fixed amount.

What function do I use to determine how long in months the money will last?