How Trigger Action/Webhook Once?

How Trigger Action/Webhook Once?

We have a Webhook Action within Zoho we want to trigger for about 350 leads (currently these 350 Leads are identified with a special field.)

We just need to trigger this Action one time for all 350 Leads, but we can't figure out how to configure a Workflow Rule to trigger for these 350 leads.

(We use Zoho Professional edition.)