Hello,
As Suresh stated, there is not a celltype in Spread that will support different formats like this. However, you can create an OwnerDrawnCellType (if you do not need to edit the text). In this case the DrawItem event will fire with a device context handle (hDC) to the cell and the rectangle of the cell. With this you can use the DrawText API or other APIs to draw whatever you want in the cell.
If you were to upgrade to version 8 of the Spread, we have added new functionality to add your own control as a celltype, so you could create a RichText control as the editor and renderer of the cell and be able to edit and render rich text. There is a sample in version 8 showing how to add a RichEdit control to a cell.
Scott S.
Product Manager, Spread ASP.NET
GrapeCity FarPoint