Need HELP with conditional usage formula

Need help creating a formula that computes the average usage for given data. I do not want to average the data; I want to average the changes in the data. My problem is that my data lines are not equal for all products on spreadsheet (one product may have 3 lines of data, and another product may have 6 lines of data). Example of one product:
data line 1 25,000
data line 2 32,000
data line 3 38,000
total change (usage) is 13,000 and my average usage is 4,333 (13,000/3)

Is there a conditional formula that will calculate my average usage for each change in product??

Thanks for any help.

Hi there,

Assuming the amounts are in Column B (change the Column reference if necessary), does the following formula help?

=(B3-B1)/COUNT(B1:B3)

Kind regards,

Robert

Assume that you have 10 dataline & all the data in Column B
This may helpful to you!
=(max(b1:b10)-min(b1:b10))/count(b1:b10)