public int GetColumnStyle(string dataFormat)
{
var numberFormat = new NumberFormat
{
FormatCode = dataFormat,
Id = 164 + NumberFormats.Count // custom number formats start from numFmtId=164
};
var cellFormat = new CellFormat
{
FormatId = numberFormat.Id,
Id = CellFormats.Count
};
NumberFormats.Add(numberFormat);
CellFormats.Add(cellFormat);
return cellFormat.Id;
}