i’m calling 
var blockCell = worksheet.Cells[
    htmlBlock.OccupiedCells.StartRow,
    htmlBlock.OccupiedCells.StartColumn
];
then just settings my html value 
blockCell.HtmlString = html; 
that equals to 
<div style="…...to the limitations of HTML rendering in Excel, which may not support...representation is critical, you could render the HTML to an image and then...