VBA help doing data validation

Additionally, you could also force C8 to be "N/A" even if the user tries to change it to yes or no after selecting one of EE_Only or EE+Child(ren):

Private Sub Worksheet_Change(ByVal Target As Range)

Application.EnableEvents = False
If Not Intersect(Target, Range("C6")) Is Nothing Then
    If Intersect(Target, Range("C6")).Value = "EE_Only" Or Intersect(Target, Range("C6")).Value = "EE+Child(ren)" Then Range("C8") = "N/A"
End If
If Not Intersect(Target, Range("C8")) Is Nothing Then
    If Range("C6").Value = "EE_Only" Or Range("C6").Value = "EE+Child(ren)" Then Range("C8") = "N/A"
End If
Application.EnableEvents = True

End Sub