In Word, select Options from the Tools menu and then go to the General tab
and check the box for "Confirm conversions at open"
Then, re-attach the data source to the mail merge main document and when you
are presented with a dialog asking you for the method by which the
connection should be made, select the DDE option. Old technology, but will
probably solve the problem.
As to why some fields are being treated differently, the reason is probably
because with the conversion method that was being used, Word considers the
first 8 or so records and from them, determines the type of data that is
contained in each field and applies that determination to the rest of the
records, which may not be correct thing for it to do.

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Hope this helps.
Please reply to the newsgroup unless you wish to avail yourself of my
services on a paid consulting basis.
Doug Robbins - Word MVP
>I am using mail merge and some of my feilds are maxing out at 255
>charactors
> and some are not why. how do I change it so the feild to not max out. I
> am
> merging for an excel doc.
If you really want the full explanation, see
http://tips.pjmsn.me.uk/t0003.htm
(Although I think at least one thing in there has probably now been fixed in
Word 2003/2007)

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Peter Jamieson
http://tips.pjmsn.me.uk
>I am using mail merge and some of my feilds are maxing out at 255
>charactors
> and some are not why. how do I change it so the feild to not max out. I
> am
> merging for an excel doc.