Hi Vaibhav,
You can try associating your tranches with the Template-entity in the ExcelImporter module. Treating this association as a one-to-one association, to can then add to your tranches amendment page the ability to select a template.
Finally, using a helper entity, add the file from the front end, and import it (see the microflow IVK_ImportTemplateDocument in the ExcelImporter module)
Hope it helps!