PPC Reports - Calculating Total Average Position

Need help with PPC report calculations

[Angelfan]

I am specifically looking for help on how to calculate the total weighted average position for all of my keywords in excel. From what I understand there isn't a designated formula to use in excel 2000. (yes I know, I need to update it) hehe.

If you know how I could do this, please help! Thanks!

Ex:
Keyword ¦ Average Position
keyword 1 - 2.5
keyword 2 - 3.8
keyword 3 - 1.1
keyword 4 - 5.6
keyword 5 - 3.6
Total Weighted Average: _ _?

[beesticles]

Weight it by the number of impressions that each keyword received.

Eg.

KW1: 1000 imps, 2.5 avg pos
KW2: 2000 imps, 3.8 avg pos

Total = ((1000 * 2.5) + (2000 * 3.8)) / 3000 = 3.4