Workflow rule conditions change

Workflow rule conditions change

I have a workflow rule that triggers when field "A" (a checkbox) is updated. The workflow sends 3 e-mails (one a week) to a prospective customer for a certain product. What I want to do is stop the workflow if the customer makes the purchase -- so they don't keep getting e-mails asking them to buy something they have already bought!

In field "B" we record the purchase. So I set up a workflow whose criteria for execution is that field "A" is updated, but with the added condition that field "B" must be empty. So if I update field A, and then 2-1/2 weeks later (after the first two e-mails have gone out) I record the sale in field "B", will the workflow continue on and send them the third weekly e-mail anyway, or will it stop working as soon as the condition on field "B" is no longer met?

Thanks.

Tony Stoltzfus