Need help with debug issue with macro

Sorry didn't read the first post thoroughly enough. The problem is you are specifying a range with no specific workbook context... try this mod and let me know?

Dim gCount As Date
'Updateby20140925
Sub Timer()
gCount = Now + TimeValue("00:00:01")
Application.OnTime gCount, "ResetTime"
End Sub
Sub ResetTime()
Dim xRng As Range
Set xRng = Application.ThisWorkbook.ActiveSheet.Range("E1")
xRng.Value = xRng.Value - TimeSerial(0, 0, 1)
If xRng.Value <= 0 Then
MsgBox "Countdown complete."
Exit Sub
End If
Call Timer
End Sub