Use XSLT to get Excel files

I need to transform xml data into an excel report. Currently i'm transforming into html format and then using the Excel object model in dotnet to provide Excel specific manipulations such as hiding and grouping of rows and columns,number formats,etc..
I know there's an Xml file format available from Office XP onwards but even that doesnt support features that i've mentioned above. Is there any other solution? It has to be a dotnet one.