Mbordelon,
you might be out of luck here using conditions. What you're asking is essentially in NS territory not DS.
I've had a quick look in DS and its default app inventory doesn't include any details for IE version.
The only thing I can think of is to put a e.g. VBscript as the first task in the installation job which checks for the existence of IE7 reg keys or files and either continues or stops depending on what it finds....

Sorry

R

Make a Filter. Application Description does not contain Internet Explorer 7. 

NOTE: You will have to tweek this until you find a good way to determine IE6 is, or IE7 is not installed. If I remember correctly IE6 does not show in inventory, but IE7 does. Use this to your advantage to make a filter.

Click on All Computers with that filter in place, then deploy.

As mentioned, this is really better handled with NS.