Nope. You can hash someone's gamertag and use that for internal comparison of someone's gamertag, But I think that would be useless for what you are trying to do.how about something like this
var [gp] = [goldpieces]
inventory [player] [add] [gp] 
would this work fine?
Nope. There are no strings in variables.
I forget the exact problem with them, But I think Craig said strings are immutable, And create a lot of garbage.
1. Strings [text] in C# are immutable and always allocated on the heap. So all string replacement/substitution must allocate a new string, on the heap, which creates garbage. A lot of garbage when it's done frequently. Too much garbage generation causes garbage collections, which cause CPU stalls for up to 500 ms. This is the main reason I changed scripts from interpreted to bytecode.
I do remember now that Craig said he could possibly create his own string type for scripts. But that isn't in the game.