To perform a script when a field is clicked, either use Button Setup... to turn the field into a button object or use the OnOBjectEnter scritp trigger.
The text field with the URL can use the Go TO URL script step to open the specified web site in the user's default web browser. A web viewer on the layout can also be set to this URL.
the Send Mail script step can be used with the field that contains an email address to open up a dialog for sending an email or that can do the entire send mail automatically with further input from the user. (Depends on what you need to have happen when the field is clicked.)
IF you are using the same field for bothy URL's and email addresses, A script can check for the presence of the @ symbol to distinguish between URL's and Email addresses. PatternCount ( YourTable::YourField ; "@" )