[UMG] Widget switcher cannot change active widget index?

Hi,

Im trying to create a dialogue box that changes text upon a button press like the zelda games,

at the moment im trying to use UMG and a switcher but the problem is I cannot access the active widget index to change what dialogue is showing on each button press.

currently im using a cast to try and control this from another blueprint, is there something im missing?

thanks in advance