.ToString("0000")

Imports System.IO

Function Exportar()
        Dim strStreamW As Stream
        Dim strStreamWriter As StreamWriter
        Dim Filas = frm_principal.Grid.Rows.Count
        Dim Columnas = frm_principal.Grid.Columns.Count
        Dim Archivo As String = Application.StartupPath & "\Centros.csv"
        Dim Linea
        Dim f, c

        File.Delete(Archivo)
        strStreamW = File.OpenWrite(Archivo)

        strStreamWriter = New StreamWriter(strStreamW, System.Text.Encoding.UTF8)

        'CABECERA
        For c = 0 To Columnas - 1
            Linea = Linea & frm_principal.Grid.Columns(c).Name & ";"
        Next

        Linea = Mid(Linea, 1, Linea.ToString.Length - 1) 
        strStreamWriter.WriteLine(Linea)
        Linea = Nothing

        'FILAS
        For f = 0 To Filas - 1
            For c = 0 To Columnas - 1
                Linea = Linea & frm_principal.Grid.Item(c, f).Value & ";"
                'MsgBox(Grid.Item(c, f).Value)
            Next
            Linea = Mid(Linea, 1, Linea.ToString.Length - 1) 
            strStreamWriter.WriteLine(Linea)
            Linea = Nothing
        Next
        strStreamWriter.Close()

        Try
            Process.Start(Archivo) 'Ejecuta el archivo creado
        Catch Ex As Exception
            MsgBox(Ex.Message, MsgBoxStyle.Critical, Ex.Source)
        End Try

    End Function

Call Exportar()

        Dim i
        Dim Columna = DataGridView1.Columns.Count

        For i = 0 To Columna - 1
            DataGridView1.Item(i, 1).Style.BackColor = Color.Aqua 'Se pinta la fila 1
        Next

DataGridView1.Item(ColumnIndex, RowIndex).Style.BackColor = Color
DataGridView1.Item(ColumnIndex, RowIndex).Style.ForeColor = Color