DefaultCellStyle.FormatProvider in DataGridView

Question

I am trying to change the currency format as the user enters in a specified cell. By Default the currency format is '$' and as the user enters in a particular cell the format changes to '₹'. But it is throwing me an error.

The code to change the format on cell value change:

private void dg_PDetails_CellValueChanged(object sender, DataGridViewCellEventArgs e)
    {
        foreach (DataGridViewRow row in dg_PDetails.Rows)
        {
            if (row.Cells[6].Value != null)
            {
                var format = (NumberFormatInfo)NumberFormatInfo.CurrentInfo.Clone();
                format.CurrencySymbol = "₹ ";
                dg_PDetails.Columns["AmountProduct"].DefaultCellStyle.FormatProvider = format;
                dg_PDetails.Columns["AmountProduct"].DefaultCellStyle.Format = "c";
            }
            else if (row.Cells[6].Value == null)
            {
                var formats = (NumberFormatInfo)NumberFormatInfo.CurrentInfo.Clone();
                formats.CurrencySymbol = "$ ";
                dg_PDetails.Columns["AmountProduct"].DefaultCellStyle.FormatProvider = formats;
                dg_PDetails.Columns["AmountProduct"].DefaultCellStyle.Format = "c";
               
            }
        }
    }

Error Img