Héé, what is wrong with my filter?

I've a code in my excel file following:
Dim X As Boolean


Private Sub Worksheet_Calculate()
Dim R As Long
If X = True Then Exit Sub
X = True
For R = 1 To Cells(65535, 3).End(xlUp).Row
Select Case Cells(R, 3).Value
Case "", 0, "C"
Me.Rows(R).Hidden = True
Case Else
Me.Rows(R).Hidden = False
End Select
Next
X = False
End Sub

But now my filter don't work anymore!

Who can help me with this problem??

Greets Berry