Quick formula question

Hi. I'm trying to create a formula that for 2 adjacent cells, it takes a quarter of their combined value and adds it to another cell and divides the combined result from a fourth cell. What I thought would work is this: =SUM(((K2:L2/4)+M2)/S2). It's giving me a "#VALUE!" message. Can someone please let me know what I'm doing wrong? I've tried variations on this with differing amounts of () brackets, but to no avail. I'm an excel newbie and would be extremely grateful for any help.