Loop running very slow

Hi Expert,

need help for optimizing the mentioned loop code.
it is running very slow.

Dim X As Integer
    Dim X1 As Range
    Dim X1a As String

    For X = 1 To 500

        For Each X1 In MSheet.Range(NamedRange)
            X1a = X1
            If ActiveCell.Value = X1 Then
                Exit For
            Else
            End If
        Next X1

        If ActiveCell.Value <> X1a Then
            If ActiveCell.Value = "" Then
                ActiveCell.Offset(1, 0).Select
            Else
                MsgBox "Invalid Entry In Cell - " + ActiveCell.Address(0, 0) + ", Please Try Again."
                Application.Undo
                Exit For
            End If
        Else
            ActiveCell.Offset(1, 0).Select
        End If

    Next X