Need help with Workflow syntax for Opportunity

Hello,

I have been trying to modify an existing workflow within our environment that currently stops users form updating an opportunity after it has passed certain sales stage (with the exception of Admin role). This workflow is working fine currently. Now the business logic has changed a little bit that the business now wants the users to be able to only update one particular field after it has passed those particular sales stage (Anticipated Order Date in this case). I have been trying to incorporate that field in the exisitng workflow but its not working. Can anyone of you tell me