ParticleMel

Hoping someone can help me with this - I've tried looking through previous posts, but can't find exactly what I'm looking for. I have 4 search fields and want to be able to leave the drop down fields blank if I don't want to include one of them in a search. When I make the field a dropdown field, the first value is always displaying in the field, and I can't make it blank or deselect that field from the search. For example, in the selection below, there are 7 provinces. I may not know what province a district is in, so I would want to search on district and name (nombre) only thanks in advance