Multiple values for custom fields provided in SOLR query

Hi,
I have a requirement in which i need to have multiple values in my custom
fields while forming the search query to SOLR. For example,
fileID is my custom field. I have defined the fileID in schema.xml as <field
name="fileID" type="string" indexed="true" stored="true" required="true"
multiValued="true"/>.
Now fileID can have multiple values like 111,222,333 etc. So will my query
be of the form,

q=+fileID:111+fileID:222+fileID:333+apple

where apple is my search query string. I tried with the above query but it
did not work. SOLR gave invalid query error.
Basically the requirement is , if fileIDs are provided as search parameter
then search should happen on the basis of fileID.

Is my approach correct or i need to do something else? Please, if immediate
help is provided then that would be great.

Regards
Suryasnat Das
Infosys.