ReplaceField method has very strange effect

[Screwtape]

Hi.

I'm generating a RTF document with JScript.

I've put a data field in the template, and am using ReplaceField to update the value just prior to calling DocumentElement. When I do this, I keep getting Bell sounds and the document had the field replaced, not with what I specified, but several element names and descriptions.

If I comment out the ReplaceField method, it all works fine and just prints the default for the data field each time.

Very strange.

Anyone suggest what I might be doing wrong?