MS Acess97 Reports – Weighted Averages e

I have created a report in MS Access. I am trying to average a column of #’s and excluding all 0 or null values. Example: There are three #’s, 10, 8, 0. When I use Avg the answer is (10+8+0)/3 = 6. I want the average to be (10+8)/2 = 9. I want the formula to exclude all records with zero it them. Help!!!!!!!
Please email me ASAP!! creatdtp@clarityconnect.com