That's how I tried doing it - but my sleeve ended up being about 6 inches too long? Actually the sleeve ended up being as long as the sweater. So I ripped in back to the completed 22 rows of seed stitch (about 4 1/2 ins itself) and decided to try again - perhaps you can tell me where I may have made the error in interpreting the pattern:
Here is the full sleeve instructions
Cast on 35 sts. Work 22 rows in seed st as given for left front, inc 2 sts even across last row. 37 sts. Work 4 ins of stocking stitch placing a marker at each end of last row. Cont in stocking st, inc 1 st each end of 5th row from marker and every following 8th row until there are 55sts. Cont even until work from marker measures 18 ins ending with rs facing for next row.
cast of 2 sts beg next 2 rows. Dec 1 st each end of needle on next and ever following alt row to 25 sts. then on every row to 11 sts. Cast off.