Setting attribute values on Open Transaction process action issues.

Summary:

I would like to set values in a specific order on Open Transaction.

Content (please ensure you mask any confidential information):

There are a few questions regarding this issue.

1. Where is the best place to implement the "setattributevalue" function? I ask this because we are not able to use this within a script that sets a value for another attribute. I have tried applying this to a library function and calling that library function inside the script that sets a value for an attribute, but does not work.
2. Setting attribute values through a function on Open Transaction does not work. The implementation was simple, have an attribute with a default value, then on Open Transaction, use the function to set the value instead of default, then add that attribute to the layout so that I can see attribute update. But, change was not happening.