can i search a mutli-value custom field as 'or' vs. 'and'?

[barry 1]

i have a list of property types in a custom field.  the values are things like 'condo' and 'townhome'.  

when someone selects both condo and townhome on the search, meaning either are ok, i would like the search to show properties that are either condo OR townhome.  the behavior of search is condo AND townhome which will always be an empty set.

..&jdfields[][118]=3&jdfields[][118]=4..

optionally, i could do it on a url for my needs.  currently above is how the search is formatted when both are selected.  is there a way on the url or in the custom field to make a search an OR?