Hide Row If Corresponding Cell In Column C Is Not Empty?

I want to hide the row when value "x" is entered in column C

I tried this code in the sheet, but nothing happens.......

VB:
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If Target.Column = 3 Then
ThisRow = Target.Row
If Not Target.Value = "" Then
ThisRow.EntireRow.Hidden = True
End If
End If
End Sub

So when a "x" is entered in cell (115,C), row 115 must be hidden. When a "x" is entered in cell((9,C) row 9 must be hidden to, and so on. When a cell in an other column is changed, the macro does not need to start.