How do I associate a custom function with a task workflow

Trying to set up the Milestone Autocomplete Custom Function. I think I have the parameters set, but the description includes this comment:

"Function has to be associated with task workflow which executes when the status field is updated."

What does that mean and how do I do it? I don't see any setting or help file that addresses this.

Zoho SalesIQ Resources

Sticky Posts
Announcing the Zoho Projects API
Today we're excited to announce the API for Zoho Projects where any developer can extend the project management and collaboration capabilities through our APIs and can build their own customized applications for their business needs. We've tried to make the API follow the REST (Representational State Transfer) principles and generate a XML/ JSON object which allows you to access / read / write Zoho Projects data from third-party systems like Google/Yahoo gadgets, web sites, billing & invoicing systems,
Have you moved to REST API?
Dear API Users, The Documentation of our Rest API is available here . All future development will be done to this version. We are deprecating the older API today. Its documentation will no longer be available and we will also be stopping the calls to this API soon. Thanks, Prasanna