export filter that checks for existance of another route?

[Paul J R]

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.