Thanks Rick,
In essence it doesn't matter where it's used, if it's used somewhere in my document I want to have it changed. Let's say I am using Helvetica today in parts of my document, could be my default font, or used in paragraph styles, or character style. Wherever I have something using Helvetica I want to have it replaced by let's say Arial.
Basically what I like to achieve with extendscript is similar to what the change font pod is offering, but I also want to have some way to play with the weight properties as some of the fonts I like to replace use weight formats not supported by the newer fonts I need to use.
Hope it's a bit more clear now,
K.