How would I set up my saved search when I want to use a workflow to update a hidden field with the value a field that is not stored (it is using a saved search sum as it's source)?

How often does it need to update?

at least once a day. I have the workflow set up but for the life of me cannot remember how to set up the saved search. Should it just show the hidden field and then the field I am sourcing as the result and the criteria be the transaction type?

Nah. I tend to do it based on time. In addition to having my workflow update the field - I update the date/time field

I have my workflow set up like this:

i.e. if that date/time field hasn't been updated in 4 hours - include it in my results.

Ok. I see what you mean. So in my workflow - in the state - I have my trigger set to Entry and the criteria is the saved search that has the criteria of the transaction type. Is this correct? Trying to figure out why the workflow is not working:

No - that's how I'd build the saved search.