Workflow with custom objects above 4 and integration event

Hello All,

Being new to CRM OD I have tried to absorb as much of the documentation as possible but I am still having trouble seeing the compete work flow. 

So please understand that I am new to CRM so the more you can elaborate(specifics) the better it be for me to understand the processes.

I am attempting to summarize a field(s) and dump the sum into another field.  Both fields are associated with different Record types

The issue I am having is that the field I am trying to summarize is a "Custom Object 04" record type.

I finally figured out that I cannot use the "joinfieldvalue " function to associate the fileds since one of the record types is CO04.