Problem with thread sinyncron. and sessionId

[Fr...@swisscom.com]

Hi to all, 
I have to implement a load test for a checkout workflow. I created a
thread group with the following threads: 
startcheckout, setinvoice, setuserdata, setconfirmation and setsummary. 
I use Webservice(SOAP) Request Samples 
Questions: 
- What do I have to do in order to have them executed sequentially in
the given order?? (I thought that checking the 
"Run each thread group separately would have helped, but it doesn't
seems so...) 

- The threads must have the same sessionID. The request data I send
contains the sessionID. 
What do I have to do in order to have the same value for all the threads
of the group? 

This is a sample of request data I send at the moment. I need that the
SessionId is the same for each thread of the group.

<?xml version="1.0" encoding="utf-8"?> 
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xmlns:xsd="http://www.w3.org/2001/XMLSchema"> 
<soap:Header> 
<ServiceAuthHeader xmlns="...."> 
<ClientId>${USER}</ClientId> 
<Password>${PASSWD}</Password> 
<SessionId>${SESSION}${__counter(TRUE,sessionCounter)}</SessionId> 
<ClientRequestId>${__counter(FALSE,requestID)}</ClientRequestId> 
</ServiceAuthHeader> 
</soap:Header> 
<soap:Body> 
<StartCheckout xmlns="....." /> 
</soap:Body> 
</soap:Envelope> 


Thanx for the help. 

Francesco