Search and custom fields

[babouz]

Hi everybody,
Here is my question :
In our website we display product reference (595959595) and we display another reference, the client reference, created by a custom fields (175.400)

I would like to know if it's also possible to search by custom fields with virtuemart search module ?

I don't want to have multiple choice or an other search module, I just want to know how to add custom fields in search plugin.

Thank you for any help !

Sincerely