Editing values in a sheet or on a token using a macro [3.5]

I'm trying to use a character's nonlethal damage as a way to link a resource to their token that isn't default supported by the 3.5 sheet (specifically, the Striker's tension from Spheres of Might). I was hoping that by doing this, I could make macros that would alter the value of their nonlethal damage, which would then change the value in the bar above their token. Then I realized that I don't actually know how to make macros edit a value in someone's character sheet. The idea is that they could use the macro, which would show the description of any ability they use along with any roll that might accompany said ability, and then subtract the relevant amount of tension from their nonlethal damage. I can do the first parts easily, not so much the last one. Ideally this would be using the standard macro templates so it looks prettier, but if that's not possible then I'll take what I can get.

Macros cannot, by themselves, change or alter values on sheets or tokens. That, for good/ill, is reserved for the API, a pro perk. If you're in a game owned by a Pro member, a script like TokenMod can alter information on a token (which could filter to the character sheet with the proper bar linking), or ChatSetAttr can alter the character sheet.

Ahhh, thank you for letting me know! This is for one of my players in the game that I'm running. I was going to get a plus account to get a bigger storage limit and dynamic lighting, so I might just go pro to use those API tools and the custom sheets. I imagine they would both be helpful if I ever want to run my own systems on here.