Desaturating Clip
You know when you've got a clip that you want a certain effect on but not the whole way through, maybe gradually occurring? for instance a gradual desaturation ie a movie clip which gradually fades to grey. the easiest way i have found is this

-imagine a 60 second clip you want to desaturate
-put it on the time line twice
-shorten the first clip on the time line by a small amount at the end
-shorten the second clip by a small amount at the start
-this could leave you with clip one -58.08 seconds
clip two -58.16 seconds
-add greyscale effect to clip two and drag it over clip one to show your fade transition bar.
-a small amount of arithmatic is required. ie 58.08+58.16=116.24
-116.24- original clip length 60 seconds= 56.24
-extend the fade bar to exactly this length (56.24seconds) you may have to zoom in for this
- hey presto with the fade at the correct length, both clips are in synch and the fade transition is now a desaturation tool ( or whatever effect you like)
-graduated effects on movie clips! simply adding and subtraction.
if something like this has been posted before .....oh well.
hope you like it. hope you could follow this