Writing custom Time Eval operation

Hi all:

I'm tasked with writing a custom Time Evaluation Operation.  I've written some for Payroll but Time is new for me.

I understand from other discussions that there is a different method for writing Time Eval operations and functions.  Does anyone have documentation on this subject?  I've seen comments about a cookbook available from SAP concerning the subject but have not found a link to it.  Note 516489 also indicates that SAP should be contacted for this but I hope by now some documentation exists on this subject.

Thanks for any help that can be provided.

Fred