Design dilemma--sleeves

I'm currently knitting myself a cardigan. The front and back are done. I thought I had finished one sleeve--enter the dilemma. After working nine inches of seed stitch I began shaping. For the sane of simplicity, I planned to decrease at the beginning and end of every second row. The result...

 a twelve inch long sleeve.
I decided this was two short. A longer sleeve was my goal.
Questions:  How will I accomplish this goal? How will I ensure that the shaping is properly placed?
Enter this helpful device...

 a row counter. As I complete row after row, I keep a record of my progress my roll to dial to the corresponding number.

I have the solution. Now I can rip out my mistake.
Happy knitting
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