I have created a custom form using the Post form. I am using the form for
our consultants to report the results of their on-site client visits. When
the consultant visits a client, they fill out the form and post it. That is
working just fine. However, when they visit the client again, I want them to
add information to the existing post, not create a brand new post. This is
so that I can total all of their hours on one form rather than having to
piece together multiple forms for the same client.

However, if they open up an existing form and add info to it, all they see
is a Post Reply button which just creates another instance of the form. How
do I set it up so that they can append info to an existing form?