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