entering multi diagnosis'

Our computer only allows us to enter 4 diagnosis codes, is there a way or a code or something we can use to get in more than four, can we use another "99213" to allow more codes or a no charge-100 code. Also if we have multiple codes such as a shot can we add "extra" codes there? Is there somehow?? Thanks, Terry

What is the reason?

Our system allows 8 codes; I bill 4 for the visit then the other four can be used to link to vaccines, labs, procedures. I have heard that the insurers only look at the first 2 codes for medical necessity and justification for the visit level that you charge but that's a rumor...