Dynamic role Assignment in Portal using Web dynpro Java?

Hi All,

We have following requirement for dynamic role assignment.

1) User Login to Portal.

2) User Clicks on Home Tab in Portal, through RFC/BAPI, get Role from Backend(ECC) and compare the role ID with Portal Object ID through UME.

Role gets assigned in Portal after comparison, if it exists in Portal.

Can you please let me know what all steps I need to do to complete the above assignment.

Thank you
Ravi