OK, I came across a problem, when trying to use something like the following:
\chapter{c1}  
\section{s1}  
\subsection{sub1}  
Q1 - foo0 
Q2  - bar0  
\subsection{sub2}  
Q3 - foo1 
Q4 - bar1  
\subsection{sub3}  
Q5 - foo2 
Q6 - bar2
So I tried. Hard. But could not get this to work. Finally, I used several counters to do the job. Not very nice but it works:
\chapter{c1}  
% init new counters Rcount and Tcount 
\newcounter{Rcount} 
\newcounter{Tcount}  
\subsection{subX}  
%Tell the list to use counter Rcount, and use a custom label (RQ-arabicnumberOfCounter) 
\begin{list}{Q-\arabic{Rcount}}{\usecounter{Rcount} \setlength{\rightmargin}{\leftmargin}} 
%since the  list environment  sets the used counter to zero, we need to use the second counter and load it into Rcount. 
  \setcounter{Rcount}{\value{Tcount}} 
  \item fooX 
  \item barX 
\end{list}  
%when the list is finished, write the value or Rcount back to the backup counter. 
\addtocounter{Tcount}{\value{Rcount}}
That’s it. Hopefully it helps somebody. For any questions, just contact me.