How to close the internal session through coding ?

Hi Friends,

I have the below requirement. Can anyone provide me the solution ?

Step1: Execute SBWP transaction (SAP Business Work Place) --> Go to Inbox --> Workflows --> Double click on workflow item --> Opens workflow item in next screen --> There is a button "Display"

Step 2: Click on Display button. It navigates to ALV of custom program. Press "Approve" button on the Application Toolbar. It triggers a workflow. Inside one of BO methods, SUBMIT and RETURN (To the same custom program) statement is written.

Once it is approved. Press Back button --> It navigates to SBWP transaction.

After processing 4 work items, it is throwing error "Maximum number of internal sessions reached".

But user does not want this. Please provide me the fix for this.

Thanks in advance.