Case record can not be closed until all child records has been closed

[Shashivardhan]

• Create Case record
• Create two incident record
• Make the Case as parent for all  four incident
• On incident Page ,i have custom field Event end date time
• This Event end date time field should be mandatory when the Incident stats move to Resolved or Close.
• Case record can not be closed until all child records has been closed
  can someone help me with script for this