Private Sub Worksheet_Activate()
Dim T(), L&, C&
T = [I3:AH10].Value
For L = 1 To 8: For C = 1 To 8
If L Mod 3 <> 0 And C Mod 3 <> 0 Then T(L, C) = IIf(IsEmpty(T(L, C)), _
IIf(IsEmpty(T(L, C + 18)), TimeSerial(7, 30, 0), Empty), Empty)
Next C, L
[I3:P10].Value = T
End Sub