How to create an extra-offset shortcut

[Rachael Thomas Carlson]

Hello everyone:

I am trying to figure out how I can create a nifty little shortcut to
write a \once \override with the ability to manipulate the extra-offset
of a grob using non-integer numbers.  What I have found works with
integers only.  I need more control over this function: I need to be
able to input decimals.

Here is what I have (which works with integers but not decimals):

\version "2.16.2"

mkMove = #(define-music-function
        (parser location x y)
        ( number? number? ) 
        #{ \once \override TextScript #'extra-offset = #(cons x y) 
        #})

Any ideas?

Thank you,
Rachael Thomas Carlson