I hope the title is clear enough? :/

Effectively, I have a graph linked to data that gets moved by a macro to make room for new data being pasted in. However, whenever the data is moved, the range of the graph moves too, therefore never plotting any new data that is moved in. I have tried entering 

='sheetname'!A:A,'sheetname'!B:B
Into the data range, however it just corrects itself to A1:A801 and then when data is pasted in, it moves again.

Any help greatly appreciated.
Thanks
Matt