[Eventing Question] Make an event increase Effort Values

Hello, I am attempting to make an event that when interacted with will increase the EVs of a Pokemon. I have tried adding the effects of the vitamins to the event but that doesn't seem to work.

Any help would be appreciated.

Maybe this can help you. I made a script (event) for Bottle Caps:
https://www.pokecommunity.com/showthread.php?t=418237