Trouble using Data Validation/Custom to prevent entries based on text in another cell

I'm attempting to use the Data Validation / Custom selection to do the following:

If cell K7 = "EDLP" (EDLP is entered via a drop-down box), I don't want people to be able to enter data in cells T7,U7,V7,W7 ...and I want to remind them why with an error message if they try to enter data in those cells.

If cell K7 is anything OTHER THAN "EDLP", they can - but don't have to - enter data in T7,U7,V7,W7.

I can't seem to get this to work.

I will also need to copy this formula down 1000 or so rows :-)

Any feedback on getting this to work would be greatly appreciated. I've attached a file for you to see...

Thanks again!