[OS X TeX] colorbox

[Alain Schremmer]

This is just a LaTeX question but I have already wasted a couple of  
hours on it. So, I hope, …

I would like to have the same highlighting effect as in

	$f(x)$\colorbox{yellow}{$\left.\right|_{x:=-3}$}

but of course, since the delimiters do not take the height of the  
front into account, with

	$\dfrac{x}{x-1}$\colorbox{yellow}{$\left.\right|_{x:=-3}$}

  the vertical bar is too short and I am not able to move \left. to  
the left of the fraction.

Hopeful regards
--schremmer