Save updating numbers in order to retreive an average

[slacknoise]

Hi,
I have a bid and an ask price linked to a financial data service provider, hence these cells are automatically updating. Now i would like to know the average of the spread say within 2 hours. This would requiere somehow that the updating numbers would be stored somehow in order to calcaulate the average. Or could i somehow emply a technique which considers the steady updating numbers and without storing them calculate an average which gets accumulated thorughout time everytime a bid or an ask changes?

thanks in advance

[ranman256]

If you are using Excel,the numbers ARE being stored anyway.
Cant you put a cell with the formula: AVERAGE("A1:A50"), and get your answer?

[slacknoise]

the problem is the numbers dont get stored, instead they are updated in the same cell so the cells are just changing.