Formulas

Hi Mei,
Welcome to the forum, Thank you for your post.
I am a little bit confussled by your question. When we talk about a 'What If" in Excel we are considering three functions these are Goal Seek, Solver and Scenarios.
However when we consider an If function we are looking for the response either True or False to a set of criteria.
I am going to give an example of using the simple What If function - Goal Seeker - if this is not correct please come back and I will show you an IF function.
Goal Seek is a Single What If function; Most spreadsheets take some input (e.g. sales and expenses) and produce some output (e.g. profit). But sometimes you'll want to do the opposite. You might want to find the input that produces a given output. (For example, find the sales that give a certain profit.) Goal Seek does this; it runs your spreadsheet in "reverse". Goal Seek works on the cell with the formula, so for example if you had =A1+A2 in cell A3 the formula would be in cell A3, if we put values into the cells i.e. A1=1, A2=2 so the answer in A3 would be 3. Using Goal Seek we can manipulate the formula to change the values in either A1 or A2 and display a new answer in A3. So we apply the Goal Seek operation to A3 as follows; Tool>Goal Seek, and in the little dialog box that appears confirm the target cell reference, insert value into the middle box in this case enter 4, and insert the cell reference of the cell you wish to change into the bottom cell, in this case we will insert A1, Activate Goal Seek and accept the result it has generated, view A1 and it should now read 2; 2+2=4, I hope that has helped, if so please click the Resolved Link if not please come back, best regards Pete