Modify status attribute based on "Approve" action

We created a new status values "Waiting for approval, Approved, Rejected". and in the action " Approve " modify tab we set the value of the status to be approved but we have 3 lvls of serial approval, And it should only be modified after the last lvl, But once the first approver approves the quote the "status" attribute gets modified to approved while the main approval status stil Pending approval.