Via code, you would add a record to the table. Replace the variables with the appropriate ones. Green denotes the form field names, red denotes the table field names.
dim rs, db
Set db = CurrentDb()
Set rs = db.OpenRecordset("TableName")
with rs
.AddNew
!ClientID = ClientID
!InvoiceID = InvoiceID
!InvoiceTotal = Total
.Update
End With
rs.Close
Alternatively, you could use an 'Append' Query to do the same.
But I'll go on record and suggest that this isn't the ideal solution. Without a lot more coding, you will end up with multiple entries for Clients and Invoices.
Why don't you just create a report that does the same thing, without needing to append to a table? Then, your information will always be current, with no duplicates.