Run script when acquiring DHCP lease?

[Laurens Vets]

Hi all,

As the subject suggests, I want to run a script when some of my OpenBSD 
machines have acquired a new DHCP lease, something similar to 
ppp.linkup.  The best I came up with was to write a script which checks 
my current ip every x minutes or so and compares that to the one x 
minutes ago.  If they don't match -> run a script which does something 
(e.g. send an email...)

Can't this be done in a simpler way on OpenBSD?

Thanks in advance

Laurens