I refer you to the thread
points won/lost lower down the first page of this forum.
As Razinao said, it would require tracking points at the start of the round, and for it to be a decent command, you'd also want to use it whenever, so live points.
Now, you would want to take into account when people buy stuff, so we'd need to track inventories and upgrades between round start and now.
That seems like an awful lot of extra effort, for a pretty unnecessary command.
You just need to be disciplined if you want to save points. Perhaps store your points in metal to stop you buying stuff!
If you're just interested in your point loss/gain you can do like I did and give yourself a specific inventory. After every round, rebuy that SAME inventory and record how many points you have. Rinse and repeat.
(Then go OTT and write a nice google spreadsheet to record things, including map, map type, point loss/gain, whether your team won/loss, came 1st, 2nd or 3rd, and general trend).