CSS: Any way to inherit or duplicate this class?

[Clownboat]

I've just written a CSS/HTML flyout menu as an addition to an existing system (EQdkp Plus, to be specific). The menu is generated by a couple PHP functions. The output is an unordered list as in this pseudocode:

<div class="menu">
<ul>
  <li>Entry
    <ul>
      <li>Submenu Entry</li>
    </ul>
  </li>
</ul>
</div>

I want to add submenu headings to my list, which is quite simple:

stuff
<li class="menuheading">Submenu Heading</li>
<li>Submenu Entry</li>
stuff

However, I want to make the headings have the same visual style as the style template that's currently in use by the system. This is where my problem lies. Every style template defines its menu headings like this:

th.smalltitle {
  font-weight: something;
  color: something;
  background-color: something;
  more stuff
}

I wish it was just .smalltitle instead of th.smalltitle; then I'd be able to simply write <li class="menuhead ing smalltitle">. And due to some limitations with both the system and HTML/CSS, I cannot use tables inside the menu. So, I need some way to inherit or copy the smalltitle class, like saying

li.menuheading inherits th.smalltitle

Is there any way to do this?

[drhowarddrfine]

I guess you are saying you don't have access to the CSS file? Otherwise you could just do:
.menuheading, th.menuheading{
the css
}

Or, do inline styling:
<li style="css stuff">

[Clownboat]

I guess you are saying you don't have access to the CSS file? Otherwise you could just do:
.menuheading, th.menuheading{
the css
}

Or, do inline styling:
<li style="css stuff">

Right. I want to make the style match the one defined in the current style's CSS. There may be any number of styles and they're based on a CSS template that I can't change, which has the th.smalltitle block that I mentioned. Suppose I don't know what values are used, just the names of the attributes that are set.

[drhowarddrfine]

Then I can't think of any way to do it. Perhaps javascript could read the values and change them using the DOM, but that's javascript