HTML Link in email Template

[wid2001]

I am creating a re-usable email template.  I am not sure if this can be done but wanted to throw it out there and see if anyone had any ideas.  I have a button with a link to a form.  The link pre-fills fields in the form with merge tags in the url.  I need to make/create a "placeholder" for one of the tags so that I can edit/insert different values as needed.  Is this possible with HTML? This all resides in PARDOT, which does have a WYSIWYG editor.  When I click on the lick I can pull up the WYSIWIG and change attributes etc.   I would love to be able to click the link and have an "Event ID" that would change the portion of the link containing "Event ID" to what I need so that when clicked it pre-fills the field on the form with the correct "Event ID".  Everything works fine, I am just trying to find a way to make it easier for the end user when utilizing the template.  Hopefully this isn't too vague and I have illustrated what I am trying to do.  

Thanks!