We have a web-to-lead form that sends the checkboxes marked "true" on the form, to mark the respective checkbox field on our Lead record as "true" (Lead Record type is called "Marketing").

We have these checkboxes field names, and API field names, respectively.

1. Friend |   Heard_About_Company_Through_Friend__c

2. Facebook |   Heard_About_Company_Through_Facebook__c

3. Google, Yahoo, Bing |   Heard_About_Company_Through_Goog_Yah_Bing__c

Our objective is to be able to create Matrix report with the first column summarized by the checkboxes marked as true, however, since they are all their own fields, for example, the first summary could only be Friend or Facebook or Google, Yahoo, Bing. Further, we want the "Total" number of records to count only unique Lead ID's (Lead records). Ideally, we would have used a multi-picklist field for capturing this from the web-to-lead form, but our developer experienced technical issues.

I was thinking maybe that we can create a multi-picklist field, called Heard About Company Through | Heard_About_Company_Through__c, and retrospectively, update the multi-picklist based on the checkboxes.

I was instructed that a basic workflow with field update would not work, and a Trigger could be appropriate.

Any one know how to create this trigger?