How to pay 2-bills to 1-vendor with 1-check?

[Fran_3]

 We get billed by one vendor weekly but pay every two weeks.We started entering each weeks bill into AP individuallyNow we want to pay two of those bills with one check.I assume this is a split transactionBut trying to do it from the check register I am unable to associate each split to a its associated bill...
The normal sequence to me (not an accountant :-) for an individual bill would be... post the bill...
Expense > Lawn            AP > pro Lawn Svc------------------------       ------------------------             | 100                    100 |             |                                  |
Pay the bill
       Checking             AP > pro Lawn Svc------------------------       ------------------------      100 |                                  |  100             |                                  |
But the below seems to do this when the bill is paid
       Checking             Liabilities > AP------------------------       ------------------------      100 |                                  |  100             |                                  |
I would have thought in the "Account" column of the register I could get to AP > Lawn but it only let's me get to AP
How can I associate the each split with a particular bill from the vendor?
Thanks for any help.  
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