OK I have found the \special{mathmlinput } command

This command at the moment is not available on all servers (for example available on wims.unice.fr but not on wims.auto.u-psud.fr). I have tried it on my personal svn version of WIMS and it is perfect ! It works with Chrome, Safari and Firefox

You can find help on this special command (on the Nice server) in possibiltés avancées (« advanced features » ?) in the createxo help section.

Yves