How to control camera zoom with a widget?

I need to use the ‘slider’ on a widget to control the zoom on player’s camera, how can I set this up?

For context: I’m setting up a level that allows the player to explore a volume using a series of menus and submenus that show (via widget) on the side of the screen while the volume (a static mesh in an otherwise empty level) shows at all times. The buttons on the menus do various things like changing camera position (actually moving the player pawn) and filtering how the volume is shown. What i need is for one of these menus to have a slider that controls the player pawn camera zoom.