Error with gravity expression

[David Rodriguez]

Is there an easy way to let me turn this off, control the position and then have the expression come back on?

So here is my final expression,

Vy0 = 200; //initial y velocity (pixels/second)
seedRandom(index,true);
Vx0 =random(-200,200); // initial x velocity (pixels/second)
g = 2500; // gravity (pixels/second/second)
floor = 1050;
e = .82; //elasticity

b = floor – position[1];
h = b + Vy0*Vy0/(2*g);
T = Vy0/g + Math.sqrt(2*h/g);

if (time < T){ y = Vy0*time - g*time*time/2 + b; }else{ Vy = -(Vy0 - g*T); while (true){ Vy *= e; t = T; T += 2*Vy/g; if (time < T){ t = time - t; y = Vy*t - g*t*t/2; break; }else if (T - t < thisComp.frameDuration){ y = 0; break; } } } [position[0] + Vx0*time, floor - y]