Auto generate number with character

Public Sub autoGenerateNo()
        Try
          
            Dim dt As New DataTable
            Dim item As String
            Dim store As Integer
            dt = objGeneral.FetchData()

            ' Dim adp As New OleDb.OleDbDataAdapter(strquery, con)
            'adp.Fill(ds)
            If (dt.Rows.Count = 0) Then
                rec = 1
            Else
                item = dt.Rows(dt.Rows.Count - 1).Item(0)
                Dim split() As String = item.Split(New [Char]() {"S"c})
                For Each item In split
                    If item.Trim <> "" Then
                        store = item

                    End If
                Next
                rec = store + 1

            End If
            TextBox1.Text = "S" & rec.ToString()
        Catch ex As Exception
            MsgBox(ex.ToString())
        End Try


    End Sub