Condoms and HIV

Reflecting on that NY Times article this morning, it occurred to me that I couldn't think of a good reason why  the doctrine of double effect doesn't permit the use of condoms to prevent the transmission of HIV within marriage.  According to the New Catholic Encyclopedia, the doctrine of double effect requires the following:

1. The act itself must be morally good or at least indifferent.
2. The agent may not positively will the bad effect but may permit it. If he could attain the good effect without the bad effect he should do so. The bad effect is sometimes said to be indirectly voluntary.
3. The good effect must flow from the action at least as immediately (in the order of causality, though not necessarily in the order of time) as the bad effect. In other words the good effect must be produced directly by the action, not by the bad effect. Otherwise the agent would be using a bad means to a good end, which is never allowed.
4. The good effect must be sufficiently desirable to compensate for the allowing of the bad effect”

Couldn't the person engaged in such a use argue that they are using condoms to block the passage of the HIV virus, not to prevent procreation (i.e., the passage of the sperm)? 

The only one of the four conditions that seems to even remotely present a problem is the first one.  I suppose someone will argue that donning a condom is intrinsically evil, but that seems incorrect to me.  It's the blocking of the sperm that the Church has taught is evil.  I'd imagine that the Church would have no objection to the use of a porous condom (one that permitted the passage of sperm), perhaps used in order to prolong the sexual act.  Presumably, if a condom were available that could somehow blocked the HIV virus but not sperm, the Church would condone it without hesitation.  Moreover, as I understand the official teaching (I'm sure someone will correct me if I'm wrong), the Church permits the use of oral contraceptives for therapeutic purposes.  The use of condoms to prevent the spread of HIV seems analogous to me.

The second requirement is easily satisifed by the use of condoms to prevent the spread of HIV and without contraceptive intent for the reasons stated above.  That is, I'm assuming the correct state of mind (i.e., a willingness to use my hypothetical high-tech condom were one available and a mere acceptance of contraception as a side-effect).

The third requirement seems to be easily satisfied since the spread of HIV is prevented by the same mechanism that blocks the passage of sperm (i.e.. a latex barrier), and  not (intermediately) by the blockage of the sperm itself.  Unless I'm misunderstanding the science of this, it would be possible (though not techincally feasible given current technology) to separate the healthy sperm from the virus in the semen and to allow the former to pass (thereby permitting procreation) without the risk (or with a greatly diminished risk) of spreading HIV.

Finally, I assume we'd all agree that the fourth criterion is satisifed.

Thoughts?