I have installed besides DT Register also Community Builder where the customers Paypal email address is allready stored in a custom field for other proposes.
With regard to the DT Register implemention, I wonder, which file(s) I need to modify (and possibily how) in order to generate a Payment Option which automatically uses the Paypay email address of the user when adding a new event. Do you have any ideas of where to start?
Or do you see other possibilities of creating individual payment options which are not beeing visible to all other registered users?
If you are saying that you store the PayPal email address in the CB profile already, then you can use that. You can sync any DT Register field with any CB profile field. Go to DT Register -> Configuration -> Profile Sync. Select the appropriate fields to sync there. Of course, make sure you have selected to integrate with Community Builder on the first tab of configuration.