how to insert variables into web service request menu

Hı everyone

Do you know how to insert variables into web service request menu moreover

I want to use some ınput variables which is goıng to be used in web service request

You can see in the example

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:core="http://core.intertech.com.tr/">
   <soapenv:Header/>
   <soapenv:Body>
      <core:SelectNotFinishedDifferenceDocumentList>
         <core:customerNumber>123456</core:customerNumber>
         <core:startDate>2010-01-01</core:startDate>
         <core:endDate>2010-12-12</core:endDate>
      </core:SelectNotFinishedDifferenceDocumentList>
   </soapenv:Body>

( red ones I put manually instead of puting manually I want to use variables in variables menu. As you see in the picture I want to put variables when I ınvoke web service (I mean Starting the process)

please feel free to ask anything about my question   e mail :yusufgokhanyavuz@hotmail.com