@bgleich, you should try editing the code section and re-post using code button 101010 so that special characters do not escape.
Based on the query posted seems like you are looking at the same data source for Adding Session and Removing Session per day for every User (unique) and then want to get the difference of their count.
PS: You seem to have two separate rex running on _raw (please share your anonymized/masked raw data and current regular expression if you want us to assist you with combining the same. Also if you can pull the Status of the log event as Adding or Removing it would help you in writing better query. Remember to post these with code button 101010 on Splunk Answers comment.
If your regular expression is working as expected, and you can figure out single rex, Please try the following query,
<your_base_search_index_and_sourcetype> host=SMD* source="D:\\Apps\\CM\\Logs\\CM_*" "CM_EMD" ("Adding Session" OR "Removing Session")
| rex "<your_regular_expression_to_extract_Server_and_UserName>"
| eval Status=case(searchmatch("Adding Session"),"Adding",searchmatch("Removing Session"),"Removing",true(),"Unknown")
| dedup date_mday Server UserName Status
| eval key=Server."-".date_mday
| chart count by key Status
| eval difference=Adding-Removing
... View more