onMouseWheel + Delta

Hey everyone,
In the MM documentation, they say the following:

[size=2]Usage[/size]

*someListener*.onMouseWheel = function ( [ *delta* [, *scrollTarget* ] ] ) { 
// your statements here
}

[size=2]Parameters[/size]

delta An optional number indicating how many lines should be scrolled for each notch the user rolls the mouse wheel. A positive delta value indicates an upward scroll; a negative value indicates a downward scroll. Typical values are from 1 to 3; faster scrolling can produce larger values.

Yet, where would I actually specify a value for delta?

If I specified a positive value for delta within the onMouseWheel function, scrolling the mouse down did not automaticaly “negativitize” the delta to cause negative scrolling. But, if I never define delta and just use delta as part of my function, the value for it fluctuates between a negative and positve value depending on the direction I scroll the mouse.

Surely there must be a way to specify the magnitude of delta somewhere and let the mousescroll function specify a positive or negative value depending on the direction of the mouse scrolling.

Thanks!
Kirupa =)