Did you try using a format switch in the field, e.g. instead of

{ MERGEFIELD mynumber }

try

{ MERGEFIELD mynumber \#0.00 }

or some such (it depends on exactly what you need).

Alternatively switch back to the connection method used by default in Word
2000, i.e. check Tools|Options|General|Confirm conversions at open, then go
through the connection process again and choose DDE when offered.

Peter Jamieson