Maybe it's time to dump data|form and use John Walkenbach's enhanced data form:
http://j-walk.com/ss/dataform/index.htm

The features say you can use dropdowns.
http://j-walk.com/ss/dataform/features.htm

And the source code is available for a small fee ($20 USA, IIRC).

Marc S. wrote:

I would like to find an option to validate my entries when using the data
form. The option I'm thinking of is to use pre-defined list of value.
Thanks for your help.

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Dave Peterson