Random Number Generator

I am using a Java Script below to randomly generate a number used for a quote number:

this.getField("Quote #").value = (Math.floor(Math.random()*Math.pow(10,13)));

It does as it should, everytime you save or close the pdf it generates a new rnadom number.  Is there a way once a copy has been saved that it saves that random number that was generated?  I am trying to use this for generating a quote number to keep on file but once it is saved and reopened it generates a new number.

Thanks for your help!