Restricted element content

Hello,
I have very simple question, but I cannot find a solution for this.
I would like to create XSD, which would describe following piece of XML:
<foo atr1="some restricted attribute">
  --limited string length (or eg. positive integer)-- 
  <bar1 />
  <bar2 />
</foo>

=element with an attribute which contains restricted content and other
elements. 

I have no problem to describe the XML without "bar" elements, but it seems
to have no solution with them.

Thanks in advance.

-Vity