Number entries in datasheet subform

[DoctorJDM]

Hi

In a subform displayed in datasheet view I need to produce an index number for rows as they're entered. The subform creates a sequence of invoices for any particular job, and given the index number I can then identify the invoices for say JobRef 1234 as 1234/1, 1234/2, etc.

I'm taking the invoice dates and amounts out into the main form showing the job details, then sending the data to a Word template.

Thanks