User First Name Only Variable?

[reefadmin]

There is a block of code that references the variable [username]. If not signed in, my store says "Welcome, Guest". If signed in, my store says "Welcome, John Doe". I was hoping to have this display only the first name of the user as opposed to first/last. I updated the variable in the code from [username] to [billing_firstname]. This variable, it seems, only works on the "My Account" page. On that page, the store displays "Welcome, John". I much prefer that but, since that variable doesn't work on the other pages, I've had to put it back to [username].

Is there any way to make only the first name of the signed in user display within frame.html? I can't seem to find a variable for that.

Thanks

reefadmin