Is there a way to create a copy button that will copy a child record and several fields and still relate to the Parent table?

Is there a way to create a copy button that will copy a child record and several fields and still relate to the Parent table? For instance i create an invoice based off a cost summary(parent table) now when i create the invoice it is created in a invoice table (child table)  related by record id from parent table (Cost Summary), i then want to add a copy button on the invoice that will create an almost identical copy and still relate to the Parent Table. Does this make sense and is it possible? i used this formula just to see if it will create a copy and not copy fields just the record id but it does not seem to be pulling over the ID it brings up a new invoice but does not show record id. URLRoot()&"db/(DB I know this)=GenCopyRecord&rid="&[Record ID#] .