help with excel macro

[lwong]

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
Dim x
For x = 1 To 1000
If Cells(1, 1) <> "" Then
Cells(2, 1) = "hi"
End If
If Cells(2, 2) <> "" Then
Cells(3, 2) = "hello"
End If
End Sub

When I run this code, the cpu become busy, what happen? thank you.