Create field date using name file

[Mirko Torrisi]

Hi folks,

Hopefully this is an easy question but I couldn't do it after several 
hours..

I created a new field (adding <field name="date" type="date" 
indexed="true" stored="true"/>) and I'd like to use name file value to 
fill out it.
The name files are like: TEXT_CRE_YYYYMMGG_X-XXX-XXX.txt or 
TEXT_CRE_YYYYMMGG_X-XXX.txt (where every X are random numbers).

I'd like to use a date field type to be able to use some group functions.


Thank in advance.
Have a nice week,

Mirko