Changing Graph Template on already created graphs.

[SPace]

Hello!

I've automaticaly created graphs for my cisco router using New Graph.
Graph Type was In/Out Bits by default.
I want to change graphs to include Total Bandwidth information.
Is it posible to change Selected Graph Template type in Graph Management from In/Out Bits to In/Out Bits with Total Bandwidth without graphs corruption?
Cause I see that both Graph Template is use data source which looks the same and the only difference is in aggregation function calculating total bandwidth. Am I wrong?
Simply changing Selected Graph Template seems to not work.
Is it possible to fix on the fly or should I recreate graphs?

Thanks in advance for any solutin.