Correlating Form Submissions to PPC vs Organic - COA

[fireflyevents]

I currently don't use a landing page model. From either Adwords or Organic you reach our site, find the event product that appeals to you, and then fill out the form. I need a way to determine which of those form submissions came from Organic Vs Paid so I can calculate my cost of customer acquisition (COA).

Via Google Analytics I can see that X amount of Organic were submitted and X of Paid. If I get 5 submissions in one day there isn't an efficient way to correlate the form submissions to the medium.

Any suggestions on an attribute method that would help me sort out COA?