How can use script to invoke a workflow synchronously ?

I currently use the following scripts to start  a workflow.. But its seems that the workflow executes asynchronously in another thread . How I can use script to execute a workflow synchronously which has the same effect when I use "Workflow Element" to call a workflow?

var workflowToExecute = System.getModule("com.vmware.library.workflow").getWorkflowById(workflowId);
var objProperties = new Properties();
objProperties.put("paramter", parameterObject);
var objWorkflowToken= workflowToExecute.execute(objProperties);