Updating Sub-from with a Main-form value during insert into function

Updating Sub-from with a Main-form value during insert into function

Hi All, 

I have an auto-num field Quote_ID in a main form and on successful submission I run a loop to update a numeric field Quote_ID in the subform of the main form. 

for each  line in Line_Items
{
line.Quote_ID=input.Quote_ID;
}

I have a workflow where I need to copy an existing Quote and make a new one, which is acomplished by creating a collection for each line items and then using that collection in the insert into function.

My challenge is that I can't find a way to update numeric field Quote_ID on the subform when creating a record this way. 

Any ideas?

Thanks,