Using VBA to pull data from different worksheets.

Hi all,
I imagine this is really simple, but I have some brain freeze right now!
I am trying to pull data from different worksheets into one. The idea is, that I have sheets where the data is populated, then the front sheet will have a drop down listbox, and a refresh button which will list all of the worksheets, (or ranges)
Hit refresh, and it will display the corresponding data, and on the right hand side, show the sum total for that data.

I could link all the cells via a formula, but I am stuck on how I will change the data range after so it populates again in the same cells, but with the new data.
I hope that makes sense!!!
I have added an attachment of the sort of thing I mean to hopefully clarify!

Any help would be greatly appreciated.
Johnny247