How to do non-random camera shake or pulsating effect.

I already know the expression for switching between random values at a fixed rate but is there an expression or quick way to tell after effects to switch between two set values? I'm trying to do a pulsating effect where the video clip scales over and over between 100 and 102 percent for a few seconds. I'd also like for it to increase and decrease in intensity over time. This isn't a shake, it's a pulse, so I don't want it to be random, it looks strange.

What i've been doing is creating individual keys, copying and pasting. This is very time consuming and so far I haven't achieved the look I want. I know it's possible but it's annoying that i can't just tell after effects to switch between those values at such and such a rate. The expression I've tried is great it's just that the values added are random.

I've also keyed in a radial blur that goes on when the video scales to 102 so it looks like a motion blur. I also have to copy and paste these values.

Anyway, I hope that makes sense and there's a quicker way to do this. BTW im using cs4