Accepting an expired Certificate.

Dear All,
I need help urgently!
 
We are accessing a webservice using HTTPAPI as a client.
We are connecting to is using HTTPS.
The Webservice is using an certificate that is expired.
As a result we are getting the error: 
SSL Handshake: (GSKit) Validity time period of the certificate is expired.
which is indeed correct.
The problem however is that we need to accept this certificate and build the 
SSL connection on it. The system using this webservice must go in production. 
Other production systems are also using this same webservice which prohibit any 
change on the certificate for a foreseeable time.
Those other sytems (non iSeries) are able to work with the expired certificate.
 
Is there anyway to make the iSeries accept this certificate?
I've found possibilities to use ExitPrograms and am investigating this but I 
have *NONE experience with that.
Does any one know if it is possible and if Yes how to do it?
I would hate to make the iSeries the showstopper for this!
 
Kind regards,
Eduard Sluis