There will be multiple name/value pairs in the hidden var, the hidden var will also be used for an "Inventory"

If anything is unclear please ask

What exactly do you want? O.o

Want us to tell you how to use it orrr....?

To start off a function that will modify the hidden var on edit profile, made for multiple vars, I'm guessing using match/replace on the value of the hidden field

Not the best code but try taking a look at Mini Profile Background Image .

A while back, it was discussed about attempting to form some standard in the way that items are stored within this hidden field. We came up with the solution of: {variable:parameters}. Where variable is something unique to your code - Eg: the code above uses: "vf_mp" as the variable, and the information to be stored is set as the parameters.

Have a read of that code above, and let me know if there's anything further you need help with.

Edit: Profile Spoler Area is a slightly better written code that does the same thing - using w_spoiler as the variable