If cell value equals then check another cell.

Hi!

Couldn't find the solution to this anywhere.

I want the macro to check four rows. (A1:A4)
If the value in the cell is "R" then it should check
if the value in cell to the right (B1:B4) is "R" too.
If not then it should color cells C1:C4 in "Sheet2"
red.

It should only check if it's "R" in the A column.
If it's anything else, or blank, it should just skip
and check the next row.

It's kinda difficult to explain. But I hope someone
here got it.