Need recommendations to override a reference type HR/SQL attribute with a Portal entry during AD Export

We need to implement an override attribute flow from Portal-->MV-->AD that will overwrite themanager set from the usual HR/SQL-->MV-->(Portal-->MV)-->AD route. Themanager attribute from AD does not need to be flown back into the OverrideManager attribute in Portal using inbound SR.

Currently considering the following, and need confirmation/ suggestions for an optimum solution

Create a reference type attribute in portal, OverrideManager.  In the AD Export SR use IIF statement to flow OverrideManagerto AD.manager if available otherwise use manager.

Thanks

B Sunny