How to return a specific formula calculation if specific text is enterd in another cell

I have tried searching for this solution for ages without any luck yet.

Example:
In cell H1 I want the formula calculation to return F1-G1 "IF" E1 has "Buy" entered, OR H1 to return G1-F1 if E1 has "Sell" entered.

I am sure there is a way of doing this but have had to resort to this post.

Thanks in advance

Zeb

=IF(E1="buy",F1-G1,If(E1="sell",G1-F1))

Returns FALSE if the E1 says neither buy or sell

yeh dats ryt Peter.M is correct

Even You can use combo box from developer tab for your Buy & sell option no one have to enter it each time simply link it to some cell and replace the"buy" & "sell"in Peter.M formula with 1 & 2.. done enjoy.

Many thanks for that Peter & San and for the quick response, appreciated.

Kind regards

Zeb