Answer:
The HR/Admin Executive will have to send the Approval to both managers. The Approval is sent first to the first Manager. Upon receipt of the Approval Notification, he executes the Approval if he or she is the right manager. If not, it is sent to the second Manager.
The Admin must also create a lookup field within the CRM to get the details of the right manager
Thereafter, he or she is to create an Assignment Rule which going forward works to automatically insert the manager in opportunity.
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