I want to use a sub-form as a way for my team to track progress and leave notes.

My goal is to use the sub-form for most transitions in the blueprint so each transition with have a during note and then an after action with a custom function. 

So the custom function should add a new sub-form line with date, user name, and notes from the during section. 

Can you help me to write a function that doesn't erase the previous sub-form lines.