Fill first value for every <select required> ?

[CowCow]

I can easily fill first value for each select by adding a standard Form Field rule:

Type=Select

Name=blank

Value=0

However, can I target only required Selects?

In css you can do `select:required` so I tried this:

Type=Select

Name=:required

Value=0

It didn't really work. I'm not sure what's happening but some of my required Select have a value and some don't.

Thanks