Require key press to answer shared line

[jaikens@teklinks.com]

We have an executive using a T42G, and we have shared another executives line to his phone per his request. However, he has had an issue where he picks up the handset to make a call on his line, and it answers an incoming call on the SCA. Is there a way to program the T42G to only answer the SCA line when you press the key, and to not answer that line when the handset if lifted?