Here's the link to the Doom9 forum-thread containing the LimitedSharpen-function.
Normally PAL doesn't need IVTC, since PAL material is usually created by speeding up 24p-film material (actually 23.976p) to 25p, instead of telecining it (which is only necessary to bring 24p to 60i-NTSC). BUT sometimes there's PAL material that wasn't created from the original 24p source, but from the telecined 60i crap... and this is usually done very crudely, with fields being blended together and other nasty stuff. You should really try Doom9 and its forums regarding this stuff. Especially the AviSynth Usage forum is pretty cool.