How to send Gratuitous ARP ?

How to send Gratuitous ARP ?

I have a situation where I want to use Gratuitous ARP to associate a new
MAC address with an established IP address. This is done for
fault-tolerance.
I have a real-time host with two MAC interfaces, but one IP address. When
the board hosting the active MAC interface goes down, the standby board
picks up. The new board has its own MAC address which it needs to broadcast
to the network.

Is there any API or ways to send the Gratuitous ARP over the network? I know
when we add the new IP address
on the interface, OS does send the Gratuitous ARP on the network. I can not
add/remove the IP address from the interface. I am working on Windows Server
2003.

I checked the IP helper functions in MSDN but without help.

Thanks in advance.
Rajesh