how does one override set child element properties

say i have a table row in IE which is generated from a query:

<tr onMouseOver="..." onMouseOut"...">
<td class="someclass">hi</td>
<td class="anotherclass">bye</td>
</tr>

the <td> elements are formatted with classes in my stylesheets... what i would like to do is temporarily override those values for the entire <tr> using mouseovers

i know the way inheritance works going down but i cant seem to get it to work going back up .... i have tried calling a script, setting an inline style on the <tr> etc.. is there an easy way to do this short of writing a script that redefines the classes i am using in the <td>s?

thanks !