Kentico Email Widget using custom contact fields

Hi,

I'm creating an email template using Kentico's email marketing module. In which I have an email widget that retrieves and fills in holiday detail parameters based on some custom contact field values therefore making this dynamic for each user.

How can I pass custom contact fields in to the widgets from the recipient? The recipient object only contains set values.

Contacts for this email campaign are collected from a form submission that passes in the required values.

<div style="display:none;">
    {% holidayDate = Recipient.GetValue("holidayDate"); #%}
    {% holidayId = Recipient.GetValue("holidayId"); %}
    {% ItineraryData = customNamespace.GetItineraryItem(holidayId, holidayDate) #%}
</div>

<h2 class="price">{% ItineraryData.GetValue("Price") #%}</div>

Something like the above is what I am trying to achieve but I can't seem to work out how to get these custom fields to use in the email widget.

Thanks, Luke