How could the record from import data to associate with subform?

How could the record from import data to associate with subform?

Dear Sirs,

I have a form call "New Order" which contains a subform is called "Order Part".
For each line in Order Part, there is a subform called "Invoice".

Invoice data is imported from an Excel.

Would you please let me know how I could link up the invoice with corresponding "Order Part"?

Please advise.

Thanks & Regards,
Clara