export filter that checks for existance of another route?

Hi All, First time post, i've been playing with bird for some time, but there is one thing i cant figure out how to do and that is use the existence of a specific route as part of a filter. for example, if the filter is processing a route to 4.3.2.0/24, check if a route to 1.2.3.4/32 (exact) exists, if so then accept, otherwise reject. Is this something that is possible? or do route filters only have the ability to check against the information thats sent to the filter itself? Thanks in advance, PJR.