Count unique instances

Production Schedule Example


This is related to my last question: I want to count how many seperate lines part "A" is running on. It could be running twice on the same line so I can't do a simple count. In the example below I would like the formula to return "3" because it is running on lines 1,2,and 3.

Thanks!

Line part run-date
1 A 7/1/2007
1 B 7/2/2007
1 A 7/3/2007
1 D 7/4/2007

2 A 7/1/2007
2 D 7/2/2007
2 C 7/3/2007
2 A 7/4/2007

3 C 7/1/2007
3 B 7/2/2007
3 D 7/3/2007
3 A 7/4/2007