Hi Andy,
I think you have to implement a script policy with onGetEffectivePolicy() handler.
In this policy, read the value of EmployeeType attribue, and then make (or don't) the attribute for account exiration date as read-only by $Request.SetEffectivePolicyInfo() and $Constants.EDS_EPI_UI_AUTO_GENERATED.
Please refer to ARS SDK for details about SetEffectivePolicyInfo & EDS_EPI_UI_AUTO_GENERATED
