Hi Jessica,
We set our site up to do this very thing, http://synthesio.com/corporate/en/resources/#guides.
We only use a couple of forms across our whole site, so in the smart campaign smart list we reference the form and the landing page the form is on. Then we have separate programs for each piece of content with sales alerts built into the flow step of each unique smart campaign.
If you are sending sales alerts, you can take a look at this article, which explains how to use the
{{SP_Send_Alert_Info}} token to include campaign details:
https://community.marketo.com/MarketoArticle?id=kA050000000LADCCA4
Then to hide the form for known visitors, you can show custom HTML using cookies. This is also in use on our page above, and then here is the support aricle that shows the details to set it up:
https://community.marketo.com/MarketoArticle?id=kA050000000LHAZCA4
Hope this helps!
Todd