Try this:

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim tmpbox As Range
application.screenupdating = false
Set tmpbox = Sheets("TargetSheet").Range("A8")
sheets("TargetSheet").Unprotect

Do Until tmpbox.Row = 26
If tmpbox.Value = "" Then
tmpbox.Offset(0, 2).Value = ""
End If
Set tmpbox = tmpbox.Offset(1, 0)
Loop
Sheets("TargetSheet").Protect

End Sub
Obviously change "TargetSheet" to the name of your sheet. let me know if this works!