hwc sup 2.1.3 issue on passing value to a mbo

Hello Experts

I am facing an issue for passing a value to the MBO in hwc sup.

I am using the below code for it .

I am writing the code in customBeforeSubmit function in Custom.js.

Here is the code below

if((screenKey === "_WelcomePage") && (destScreenKey === "DestinationScreen"))

    {

        var formWelcome1 = document.forms["DestinationInfoForm"];

        if (formWelcome1)

        {

        alert(123654123);

             alert(" In Payment Tracker "+"123654123");

formWelcome1.arg2.value = "123654123";// masterSessionId;

        }

    }

Please share some idea regarding this issue?

Thanks

Anil