I have a workflow in a list to create date entries in the calendar based on a value in a list field. The workflow is triggered on item creation or change.

This has the side effect of creating multiple list items. Any ideas how to check if one already exists?

Hello,

You can add one condition before creating new one like:

If Title "is not equals to" "provide same name of event"

Then add new entry.

You can use any field value for comparing.

Hope it could help