Calculations do I use IF Statements? If not what please?

Hello
I'm having a bit of a problem writing an IF statement. By that I mean I think I need an IF statement, but Im not sure. I really need some guidance.
I have a spreadsheet which is calculating the price of cheese.
I can set an exchange rate which I can change.
What I need to be able to do is if the price per kilo rises by 10p then I need the Average monthly sales figures to drop by 20 and if the exchange rate drops below 0.7 then the sales increase by a similar amount.
I would be super greatful if sombody could give me some pointers on how to solve this!

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Yossi, I assume by 20, you mean the number 20, and not 20%. Here's an example of how to do what you're looking for.

Was going to post the file, but my browser won't let me for some reason. Here's what to do to the file you posted:

In cell B10 insert: =IF(B9<0.7,1,0)
In cell C3 insert: =IF(D2>=(10+B2),900-20,900)+20*$B$10

Cells C3 through C6 can have the same formula as C2, just change it to reference the right rows.

If you have questions, let me know.