double KeyFader (object obj, frame start, frame end, channel chan, double value )

Return Value: 1.0 for success, 0.0 for failure

Arguments:

Fades out the procedural ( i.e. expression driven, IK, effects driven etc. ) motion of an item in the given range. A value of 1.0 indicates that the procedural animation is completely faded out. 

Note:  This function only affects procedural motion that is processed before this function, any procedural motion added after this function (i.e. lower in the expression stack) will still affect the object.