LS9 Security String Functions

I am new to Lawson Security and I am surprised by the lack of basic common string functions available for use in rules.  Functions like len() and instr() for string length and position of a string within a string. There is an instr() function but it only returns a boolean if the search string is found.  I am trying to parse the parts of a Accounting Unit using substring and due to the fact that some accounting units are ww.xxxx.yyzzzz and some are ww.x.yyzzzz and some are just ww.xxxx, you get an error if you try to substring character positions that are not there.  I need to be able to test the length of the Accounting Unit string or the position of the '.' delimioters in the Accounting Unit.
In searching through this forum, I found a post that implies that you can use javascript in rules or possibly create user functions with javascript that can be used in rules.  
Does anyone know if thats true and if so, is there any documentation anywhere on how to do it?