Do something with every player that doesnt have a specific effect

Hello,
I am trying to make a Key that enables/disables a time freeze. I want to freeze every Player that doesn't have a specific effect. I just want to know how to give an effect(slowness) to every player that doesn't have a custom effect(slowmoeffect).

rn i have: (slowmokeypressed procedure)

if not has 'Event/target entity' active potion 'slowmoeffect'

do Execute command / 'tick freeze' at x y z

do attempt to override motion vector of 'Event/target entity' to vx: '0' vy: '0' vz: '0'