How would I write a formula to show (for example) the contents of A3 in A1 if A2 is within a stated bracketed value relative to A4?

For example inputting in A1, IF(A2=+-1ofA4;A3;"") The "+-1ofA4" bit is what I don't know. The result should be if the number in A2 is plus or minus 1 from the value in A4 then A3 is shown in A1, otherwise blank.

Thanks.