Menu field – not active

Hello, I am using the Cathe Flames theme (www.triopetra.com.gr), and i would appreciate some help. At the “Menu” bar, i have a field (for example "retreats calendar 2016", which has submenus scrolling down (for example "April 2016", "May 2016", etc). When someone clicks on the main menu title ("retreats calendar 2016"), i don't wannt there to be any action. Nothing should happen. Only when someone clicks on the submenus (for example on "May 2016"), only then they could be directed to the submenu link. HOw can i disable the action of the title on a main menu field? Thank you in advance! Eirini