How can we use synchronous Datasource operations in SmartGWT?

Question

I am new to use/learn SmartGWT and stuck with a problem regarding Datasource. I have a Datasource fetch operation and the value I get from DSCallBack of this is processed in subsequent logic. But since the Datasource operations are asynchronous, am sometimes left with blank/null values.

Let me know if I am doing something wrong or if there is a way to do Synchronous calls to Datasource.

    private String setRoleField(String attribute) {
        Criteria rolefetchCriteria = new Criteria();
        rolefetchCriteria.addCriteria("searchFlag", 1);
        rolefetchCriteria.addCriteria("Contact_ID", attribute);

        requestProperties =new DSRequest();     
        requestProperties.setOperationId("outletRoleFetch");

        DataSource.get("recently_accessed_module").fetchData(rolefetchCriteria, new DSCallback() 
        {
            @Override
            public void execute(DSResponse dsResponse, Object data,
                    DSRequest dsRequest) {

                // TODO Auto-generated method stub  

                Record[] record = dsResponse.getData(); 
                outletRole = "";
                for(Record singlerecord: record)
                    outletRole += "<font class='overview-subtitle'>"+singlerecord.getAttribute("OutletName")+"</font><font class='overview-time-label'>"+ singlerecord.getAttribute("Role")+"</font>";  

            }

      },requestProperties); 

return outletRole;
    }

This code is always returning me "" empty value.

Thanks in advance, Manoj