How to specify the absolute postion in prosper?

Switched from PPT to prosper do take me some time but 
the prosper is really a good package!

But I always cannot find the exact position to put 
the figure in. Then I keep modifing \vspace and
\hspace
to find the right place. I thought I waste time on
this.
There must be other way to do it simply.

I want to show few figures in one slide in the same
position like this:

.....
\begin{psclip}{\psframe[linecolor=red,fillcolor=white,fillstyle=solid]%
	       (1.0cm,0.55cm)(10.0cm,-6.8cm)}%
\vspace{-.8cm}
\begin{figure} 
\centerline{%
\psfig{figure=a.ps,height=7.2cm}}%
\onlySlide{2}{ \vspace{???cm}\hsspace{??cm}
\psfig{figure=b.ps,height=7.2cm}}
....
\end{figure}%
\end{psclip}

It is too boring to adjust the place. Are there
anyother better way? By the way, can one specify the
absolute postion to put figures in? How was the 
cooridinates in prosper defined? 

Thanks a lot!


		
__________________________________ 
Do you Yahoo!? 
Yahoo! Mail - Helps protect you from nasty viruses. 
http://promotions.yahoo.com/new_mail


-------------------------------------------------------
This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting
Tool for open source databases. Create drag-&-drop reports. Save time
by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc.
Download a FREE copy at http://www.intelliview.com/go/osdn_nl