Visual Basic para Aplicaciones - error 91 (variable de objeto o with no establecido)

Private Sub BT_MODIFICAR_Click()

Dim fila As Object

Dim linea As Integer

valor_buscado = Me.txt_lote

Set fila = Sheets("BD").Range("A:A").Find(valor_buscado, lookat:=xlWhole)

linea = fila.Row

MsgBox (linea)

Dim fila As Long

valor_buscado = Me.txt_lote

fila = Sheets("BD").Range("A:A").Find(valor_buscado, lookat:=xlWhole)

MsgBox fila

Dim fila

Dim linea As Long

valor_buscado = Me.txt_lote

 linea=0

With Sheets("BD").Range("A:A")

Set fila = .Find(valor_buscado, Lookat:=xlWhole)

 If Not fila Is Nothing Then

           linea = fila.Row

        End If

   End With

MsgBox (linea)

Dim fila

Dim linea As Long

valor_buscado = Me.txt_lote

 linea = 0

With Sheets("BD").Range("A1:A1000000") ' o tambien With Sheets("BD").Range("A1:A" & Sheets("BD").Range("A" & Rows.Count).End(xlUp).Row)

Set fila = .Find(valor_buscado, Lookat:=xlWhole)

 If Not fila Is Nothing Then

    linea = fila.Row

 End If

End With

MsgBox (linea)