Video editing, how to make blur value a function of the time? My goal is to make the blur filter value, size X for instance, changing while the movie plays. 
I want the blur going up and down in time like a sinus function, for instance size_X = 1 + sin(time).

So, I right clicked onto the size X value of in the blur filter of the video sequence editor and added a driver. 
Then, I went into the graph editor under drivers.

But from this point on, I do not know what to do, in order to make the time of the video clip the variable of the driver.
Why not use the cyclic function in the F-fcurve editor? Make 3 keyframes, 0,1,0 then extrapolate modifier cyclic.



Then you can spread them apart with scale S-key, constrain horizontal with X key