you forgot to type what was =< 10 mins.
This should work for you:
=IF(AND(D3-D2=0.00347222222,D3-D2<=0.00694444444,A2=A3,E2<E3),IF(E2<E3,CONCATE*N ATE(E2,E3),CONCATENATE(E3,E2)),)

fish wrote:
This might take a while to explain: I am not all that familiar with
excel.

In column A have a number (representing an area- from 1-14). In column
D, I have the time. In column E, I have a code. I want to find out how
many times any code is found with another code in the same area in the
space of 5-10 minutes (=5 mins, =<10 mins). There can only be a
maximum of two codes in an area at one time. If two codes are found in
that time range, then I want to concatenate the codes.

I previously did this in column F for =<5 mins (which is 0.00347222222
expressed in days).

in column F I typed:
=IF(AND(D3-D2<=0.00347222222,A2=A3,E2<E3),IF(E2<E3,CONCATENA TE(E2,E3),CONCATENATE(E3,E2)),)

This worked fine!

For between =5 mins and =<10 mins (expressed in days) I typed:
=IF(AND(D3-D2=0.00347222222,<=0.00694444444,A2=A3,E2<E3),IF (E2<E3,CONCATENATE(E2,E3),CONCATENATE(E3,E2)),)

It doesn't work! Why? What do you suggest?