OK, try this.

Code:
    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        Try
            Dim PathPattern As String = "^(([a-zA-Z]:|\\)\\)?(((\.)|(\.\.)|([^\\/:\*\?""\|<>\. ](([^\\/:\*\?""\|<>\. ])|([^\\/:\*\?""\|<>]*[^\\/:\*\?""\|<>\. ]))?))\\)*[^\\/:\*\?""\|<>\. ](([^\\/:\*\?""\|<>\. ])|([^\\/:\*\?""\|<>]*[^\\/:\*\?""\|<>\. ]))?$"
            If System.Text.RegularExpressions.Regex.IsMatch(TextBox1.Text, PathPattern) Then
                Debug.Print("True")
            Else
                Debug.Print("False")
            End If
        Catch ex As Exception
            Debug.Print("Exception")
        End Try
    End Sub