Need to delay boot until DHCP client is successful in connecting to a serve

All,
I am running RH9.0 I am developing an application that must have obtained an IPAddress via a DHCP client in order to behave properly. If the system cannot obtain an IPAddress via a DHCP client, I need the system to keep trying periodically. How can I set this up?
Also, I need to be able to detect if/when the LAN connection goes away. I will again, pause my application until the LAN connection returns. How can I determine this?
Thanks for your help…