title: Parameterizing the JSON Data file in the VuGen
body: <p>Need some help in LoadRunner scripting in REST API. In my requirement, I'm passing the JSON file in the <code>web_custom_request</code> LR Function,
  Following is the content of the JSON File</p>
  
  <pre><code>{"serviceLayerOperationRequest":{
     "contextObjectId": "36045467715",
     "payload":"{\"UserSessionSearchCriteria\":{\"os_st_id\":\"36045467715\",\"LastName\":\"test\",\"FirstName\":\"test\"}}",                
     "operationLabel": "CustomerSearch",
     "serviceOpInvocationId": "1111111",
     "sessionId": "{SessionID}"
  }}
  </code></pre>
  
  <p>New Value is fetched from the previous response body and successfully written into the Parameter <code>SessionID</code></p>
  
  <p>Currently, it picks the string {SessionID}.<br>
  In the above JSON file, variable sessionId's value is dynamic, so I want to parameterize it from the Parameters. What should be the correct syntax for this?</p>