Converting WMV to SVCD with AviSynth + TMPGEnc with IVTC

[DRP]

I have a bunch of 29.97 WMV I want to convert to PAL SVCD. Here's the AviSynth script I'm using so far:

LoadPlugin("C:\Program Files\AutoGK\DGMPGDec\DGDecode.dll")
# LoadPlugin("C:\Program Files\AutoGK\AviSynth\plugins\Decomb521.dll")
DirectShowsource("C:\Documents and Settings\Temp\Encoding\filename.wmv")
# Crop(0,4,-0,-4)
Lanczos4Resize(448,538)

That's working good so far but it does nothing about the required IVTC. I can just tell TMPGEnc to create a 25fps output which it does, but it does it by just dropping a chunk of frames every so often to catch up. The end result plays but you get a jump every now and then when TMPGEnc has dumped frames.

How do I perform a high quality IVTC on the WMV with AviSynth to feed into TMPGEnc?

[DRP]

So no-one here has any idea how to IVTC a WMV then? I'm amazed.