Change projectile velocity in area

Hello together,
I hope you can help me with my problem.

I’m currently try to create a kind of slow motion effect for my projectiles.
My plan is to create a multiplayer game where you can shoot at each other.
When player1 shoots the projectile it has the normal projectile speed, until it enters an sphere around player2.
When entering this sphere the projectile speed should change relating to if player2 is moving or not.
This should happen vise versa to the player1 with projectiles created by player2.

I’m pretty new to the whole topic and got my inspiration for the slowmotion here:


The thing is I want to implement it into a multiplayer game and I think changing the time is not the best idea for that.

Also the guide tells me to use an impulse insted of setting the velocity. I thougt by using the velocity I can later change the speed/velocity inside the sphere.

Looking forward for your help.
Paul

p.s if you need more information let me know