Need to bring the entities selected in prompt to the header dynamically

In EPM Cloud Management Report, we have a specific need to bring the Entities selected in the prompt.

The Entity dimension is placed in a single column having Multi Select enabled. In order to sum the entities chosen in the prompt, we have added a formula column. Now, in the header, if I use the function MemberAlias as "MemberAlias("Entity", C(A), C(B)……), I'm able to achieve the ask. However, that is not dynamic and so we are looking for a dynamic solution to bring up multiple entities selected in the prompt to the header. Attached screenshot for your reference.