Check of fields between forms

Check of fields between forms

Hello,

I am starting with Zoho and I'm having great time.

I have created two forms.
One is for contacts with several fields including Name and Company.
Second is for event with several fields including Name and Company.

The user must fill first the Contact form (no problem with this).
Then each time he fills the Event form with a new event, I want to check that the couple (Name, Company) is existing in the Contact form.
How do I do that?

Thanks
Jean