No , I’m afraid this calls for another (new) command, like Bernadette proposed something like \special{mathml ….}
However you work on wims-phtml directly, you can simply use use
\begin{html}
<span xmlns="http://www.w3.org/1999/xhtml">
<textarea xmlns="http://www.w3.org/1999/xhtml" id="mathml0" size="5" style="vertical-align:middle;overflow:hidden;resize:none;color:red" >?</textarea>
</span>
\end{html}or even better, use
\input{0}{5}{color:red}{?}{0} which generates the dame code as above
and use some simple javascript function to read the inputfield.
The « \input » may be used anywhere in latex (fractions,matrix etc etc etc)
The \begin{html}\end{html} may include any valid html-thing (images, etc), as long as you tell the system it’s encoding / namespace is xmlns= »http://www.w3.org/1999/xhtml »
joke