InfoPath Dev

I have a custom workflow that I'm building and the InfoPath form the user fills out is a broswer based form.  There is a requirement to present a drop down list of choices that is based on a SharePoint list within the same site as the form library.  While this is easy enough, I need to be able to filter the list down to list items that match a defined criteria.  Based, as a means of filling out the form, the user is required to pick a department.  Doing so needs to cause the drop down to be filled with list items for that department.  I know that I will have to have a department column in the list, but how should I go about querying the list for specific items?  Keep in mind, the list would contain over 600 items.

Thanks for any help you can provide.

You cannot query a secondary data connection, but you can use filters.  It will pull all 600 each time but you can only display the ones you want with a filter. 

So you would want to filter the data for your drop down where department name = the department selected by the user.