Need help with IF statement, possibly a macro

Hi everyone! I'm new here. I can't get Excel to do what I want it to for this spreadsheet at work. Basically, if I put a number in cell A1 I want a few other cells to turn the color yellow and an "X" to be placed in other cells. Cell A1 can have either a 1, 2, 3 or 4 placed in it.

If A1 = 1, I want cell B1 to turn yellow and an "X" be placed in C1.
If A1 = 2, I want cells B1 & B2 to turn yellow and an "X" be placed in cells C1 & C2.
If A1 = 3, I want cells B1, B2 & B3 to turn yellow and an "X" be placed in cells C1, C2 & C3.
If A1 = 4, I want cells B1, B2, B3 & B4 to turn yellow and an "X" be placed in cells C1, C2, C3 & C4.

I hope that makes sense. Is this something that can be achieve through IF statements or am I looking at a macro? I have Excel 2003. Thank you in advance.

Chris