Matching Forumbee users with data base in survey tool?

Hi,
As Forumbee doesn't contain a survey tool I need to send users to a third party tool. Is there a way of individualizing users so I can match them against a database in the survey tool? Here is an example scenario:
Let's say I invite new users to Forumbee; the first thing I will do is to post a link to a short onboarding questionnaire. The users are redirected to 3rd party tool to answer a quick profiling-Q which is stored in the 3rd part tool. 
In the next phase I want to engage users in a topic and then ask them to answer a short survey about a certain topics. Like before, I will post a link to 3rd part tool where they will take the survey. Now, I want each questionnaire to be matched against the data base with the background variables from the onboarding questionnaire. 
For this to work, I need to individualize each user when they click the survey link.
Is there a solution to this? Or a possible workaround?
/Ulf