I found somewhere that you could exclude dates by going:

For Each Rng In Cells.SpecialCells(xlCellTypeConstants, xlNumbers)
If Not IsDate(Rng.Value) Then Rng.ClearContents
Next Rng

Can I combine this with the insert blue & 0 as below:

With rng
.Value = 0
.Font.ColorIndex = 5
End With