Be specific about the constraint
A whole day away and an unavailable evening need different treatment. Use a dated whole-day or partial-day record so the constraint has a clear scope.
Manage Changing Availability
Keep changing availability out of scattered messages.
When staff availability changes, capture the time window and use it during selection rather than asking managers to remember every conversation.
Register interestRecheck when the assignment is made
Information can change between planning and saving. Staff selection and validation check the proposed shift against the relevant information.
Keep a route for urgent changes
Software helps make constraints visible but cannot negotiate cover for you. Combine the recorded availability with your normal process for last-minute conversations.