Iqbal, Miruna's right in that you can't popup a metadata window for the user but there are other strategies that you can use. First, you can trigger an email that reminds a user of things they should be filling in and wait for them. Second, you can trigger a new forms process to give a form to the user to fill out. They would also get an email which would take them into Forms to fill in further info. Finally, you could use dynamic fields to change possible entries in fields within the original metadata entry so the user can enter all appropriate info in the original entry.