You can use a different yarn, as long as the weight/guage is the same.
If the pattern doesn't give the total number of yards needed, you should calculate how much the original yarn has (X balls of that are 100(whatever) yds each = XX yds of yarn) and make sure the new yarn you are using has the same number of yards.
Mirl56 at Ravelry, too.
Learn from the mistakes of others. You canít live long enough to make them all yourself. Eleanor Roosevelt
Lady Feb Sweater
more shawlettes, socks