Mandatory Multiple Attachment for a Record

Hi, 

I have a use case where I have to attach the multiple attachment for a record and if the attachment is not attached then it should not allowed user to save the record. 

However, I have created a separate table for storing attachments and formula url button in parent table which redirects the user to the child table to create the record for Attachment and created dynamic form rule if Attachment required =yes and  #of Attachment =0 abort save.

But the issue is if user have provided all the details and missed to attach the attachment it is not allowing user to redirect to another page for adding attachment without saving the record and record cannot be saved because user has missed the attachment and if user wants to attach attachment they have to refresh the page first which results in loosing all the data which user has filled in the form. 
If I change the URL properties to popup window then also attachment will not be visible until user refresh the page. 

Kindly suggest the better way to add multiple attachment for a record, even user missed the attachment it should not allowed them to save and let them add attachment without refreshing the page. 

Thanks