dblink and insert?

I want to ghave a driger from host1, database1, table1 to host2,
database2, table2. To insert the same row into table2 only if the row
matches certain conditions. I am not clear how to write dblink
function to do that.

Can someone ofer a piece of code to put inside of my trigger function
on host1, database1, table1. I tried different variations and all of
them fail. Or db link only reliably works on selects? by the way I am
using postgresql 8.3.