Hello Vallery,
I use Excel to manage extra bits of information for description bubbles in each collection, such as codes and URLs for online CGI scripts and URLs for websites.
I then use VBA in Excel to generate the KML. As it runs through each placemark, it generates descriptions based on whether certain information exists. (For example, some of the SNCF stations link to station-details pages on the SNCF website, whilst some have no online reference and others still have live arrival links but no station details.)
Whilst Excel can produce XML output itself, by default it's full of extra Excel-added tags and it can't handle the application logic I need to produce the description bubbles (unless I put descriptions in the cells, and that would be a awful to manage).
It's a bit fiddly when I need to update a view in the GE Client - I then have to convert new output to Excel and match the new co-orinates with the supplimentary data - but I've a script to do this as well

I can't find a way of getting a VBA script to output data encoded as UTF-8, so I have to open the output in notepad.exe and re-save choosing UTF-8.
Not the most elegant solutiuon but it works well enough!
Cheers,
Simon.