Add a \# "0.000%" formatting switch inside the closing } that is displayed
when you toggle on the field codes using Alt+F9
You may need to use a construction such as { = { MERGEFIELD "Average" } *
100 \# "0.000%" } or some other multiplier to get the correct percentage.

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Hope this helps
Doug Robbins - Word MVP
> I am using an Excel spreadsheet as the datasource for
> batting avg, etc. How can I control the format of the
> merged fields to show as 9.999%? Currently a 1.000
> average shows as 1 and a 0.666 average shows as
> 0.666666666. The source fields in the spreadsheet are
> already formatted to 3 decimal places. Thanks!