My understanding of your question is this:
After a meeting has taken place, someone creates a new meeting report by filling in an InfoPath form. In this form you select a user. When you submit the form a task list item needs to be created automatically and assigned to the selected user.
Is this correct? If so, I would definately NOT use VSTA (code behind for InfoPath forms) as Novice suggests. Instead, I would either write a workflow (strongly recommended if you want something else to automatically happen when the user completes the task) or an EventReceiver. Another alternative would be to write a Timer Job that periodically processes your document library with InfoPath forms and creates the task list items.
I am not sure, but you might be able to get away with a SharePoint Designer workflow, which requires the least amount of coding.