Can I knit a sweater starting with swatch?

I was lucky to make it to my favorite yarn source's annual warehouse sale. I drove into Point on Weds night, the sale started at 7am that morning. They advertised over 15,000 skeins of yarn. To my dismay (and I figured this would happen) all of or most of the yarn is acrylic. The wool and blends was very limited, in fact less than I have seen in years past. I was able to pull together enough for 2 sweaters and got a couple skeins of odds and ends to join into my stash for hats and color work. Anyway, I started to swatch the new nob hill yarn I got. Since have 12" circulars in every size now, I can quickly make a swatch in the round. I cast on 40 stitches and looking at it as I was going it looked very close to the sleeve width for Blue sea which is sitting on the table. I decided to continue and start adding stitches for a sleeve. Now I am going to use EZ's method somewhat backwards and see if I get a sweater that fits. The yarn is thick and I am using size 8 needles, it should go quickly. I am going to knit it plain with no pattern and design. Colleen says I should take a break from two color knitting. I will post my progress. Colleen how is your sweater coming?