VB Script search within a column in one Wb and find in another WB and Highlight yellow

I get an error still. "out of range"

Sub DixieDiver()
Dim x As String
Dim i As Long
Dim y As Range
Workbooks("Missing PI Tags 20141021b.xlsx").Sheets("Jacobs").Activate
For i = 1 To 500
    x = Range("A" & i).Value
        Set y = Workbooks("DB (Old App).xlsx").Sheets("DB (Old App)").Columns(1).Find(x, LookIn:=xlValues, lookat:=xlWhole)
            If Not y Is Nothing Then
                Workbooks("DB (Old App).xlsx").Sheets("DB (Old App)").Cells(y.Row, y.Column).Interior.ColorIndex = 6
            End If
        Set y = Nothing
Next i

End Sub