I have a French version of Microsoft Office. After installing ChemOffice, I do not see the ChemOffice Add-Ins in the list of Add-Ins within Excel.
You should be able load the Add-Ins manually. To do so, open the Tools menu, choose Add-Ins, and click on the Browse button in that dialog box to find them. They are located in your C:\Program Files\Microsoft Office\Office10\Library folder. (or Microsoft Office\Office\Library for older versions of MS Office) Add the cfxl.xla, C3dxl.xla, cscombi.xla, and csonline.xla files to Excel.
The reason they did not show up is because the French version does not have a Library folder. It uses a different folder (MacroLib). So your Excel is looking in a different folder for our XLA files.