You can use the Upstream Trace tool in InfoSewer to find the upstream nodes and links from any link in InfoSewer. Once you have the upstream traced network, access the traced upstream nodes and links to the domain. Once you have the domain then these steps will allow you to calculate the proportion of flows from each upstream node and map the proportion using Map Display.
Step 1. Use the Tool Trace Upstream Network to find and make a Domain out of the Traced upstream Network
Step 2. The Traced Upstream Network
Step 3. Use the created domain in Output Report Tabular Reports
More in the attached PDF File How to Find the Proportional loading to a Link or Manhole in InfoSewer.