Creating a simple IF-THEN formula

I'm almost embarrassed to ask this, but I have searched the "iWork Formula and Function Help" in vain, and any similar questions asked in these forums are complex and really unrelated to what I need to do. What is the basic syntax for an IF-THEN formula in Numbers 09?

For example: I want one cell to show the sum of two other cells, but if that sum is over a certain limit, I want it to show the limit. In other words I want to tell Numbers something like this: "If C1 plus C2 are less than 24, enter the sum of C1 plus C2. If their sum is more than 24, enter 24." I've been looking for two hours now, and I simply cannot find anything that gives me the basic syntax to such a statement, certainly not in "iWork Formula and Function Help." Please help if you can. Thanks.