・シート

Dim c As Range

Dim rn As String

    Set c = Sheets("取引先住所マスタ").Range("A:A").Find(What:=UserForm2.TextBox3, LookIn:=xlValues, LookAT:=xlWhole)

   rn = Sheets("取引先住所マスタ").Range("A:A").Find(c).Row

・フォーム    

Dim myTarget As Range

    Dim myFind As Range

    Set myFind = wb_B_TMJ.Range("A:A")

    Set myTarget = myFind.Find(UserForm6.TextBox1.Text, LookAT:=xlWhole)

  myTarget.Activate

  Dim R As Long

        R = ActiveCell.Row

・別ブック

Dim a As String

  Set wb_B = Workbooks("取引先マスタ.xlsm")

  Set wb_B_TMJ = wb_B.Worksheets("取引先住所マスタ")

  Set wb_B_TMK = wb_B.Worksheets("取引先口座マスタ")

        i = wb_B_TMJ.Range("A1").End(xlDown).Row

        a = UserForm4.TextBox2.Value

        Dim mycell As Range

        Set mycell = wb_B_TMJ.Range("C2:C" & i).Find(What:=a, LookAT:=xlWhole)

        If Not mycell Is Nothing Then

                MsgBox "社名が存在しています。ご確認ください。"

        Else

                'MsgBox "未登録番号です。登録しました。"

                住所登録3

        End If