I think I can help here as I just completed a dog sweater a few months ago and the pattern sounds familiar. For your next row, work across 5 stitches, ignore the bound off section, drop this yarn now and using seperate yarn, work the middle section, then ignore the bind off part, attach new yarn and work across 5 stitches (I'm assuming there are 5 on each side), using the same needles for all three sections. On the next row, work across five stitches, then with second yarn work across middle section, then with third yarn work 5 stitches, same needles. Keep going until it measure 1 1/2 inches from bound off row ending with right side facing for the next row. Next should be the closing row. No more yarn changes with this, just work 5 stitches, add on ___? stitches (whatever your pattern says), don't change yarns, use the same yarn for the middle section and work the middle section, then add on ? stitches, then work 5 using the same yarn you used when you started this row.
Hope this helps,