Are you doing decreases for raglan sleeves? Usually you just keep all the stitches in the pattern except for the three or four edge stitches where you work the decreases. As you decrease your cable will get smaller from one side and eventually you won't be able to cross it anymore.
For example if you have a 6 stitch wide cable, you may just be able to cross five stitches once the edging starts to "invade" the cable. After the next decrease you'll only have 4 stitches from the cable left (and probably won't want to cross it right at the edge - it can get bulky). After the next decrease you'll be down to 3 stitches, etc.
I usually like to do a 2 stitch stockinette border and the SSK on the right edge, follow pattern across to last 4 stitches, K2 tog, K2 at left edge.
Hope this helped a little.