He wants a way to record this data, he's not asking us to generate it.
My best guess on how to do it would be to get an application like MSI Afterburner (GPU overclocking tool, it also monitors stuff like temp,% usage and clockspeed) and find some way for it to export its results as raw data, and then import that into an Excel sheet to turn into a graph. I dont have Afterburner or any overclocking programs on my computer so I dont know if it can do that natively, but given your creating what is essentially an auto-overclock tool by the looks of it, I think you might be able to code up a solution for it.