The directory button on the phone actually reflects upon the directory url in the enterperise parameters (or in case you set it on a phone, the url in the phone will be taken).
It appears to me that you misunderstand how parameters work. If you define parameters, when a user subscribes to a service (via his personal page(http://callmanager/ccmuser)) he/she has to enter the value of these parameters - and they are then set automatically when the service is launched.
Those aren't parameters that are asked for when a user actually accesses the service.. the point of having them configured is so that they are entered once - not per session. .If you want per session, you need to write your own login page and have the service point to that login page, collect the parameters, then launch the existing page with the appropriate parameters set.
Now in case of the directory url, all this is moot.. the service url remains static, and it has nothing to do with services, so even if you subscribe a user to a service and set all the parameters, the url called when the user presses the directory button is the url as defined in the enterperise parameters/on the phone. You can't even use the ?device=#DEVICENAME# shortcut (at least it used to be like that for the idle url.).
Thus, if you are refering to the personal address book as I think you are, then you'll have to add some logic to the page you call from the directory button url: you'll have to look up the IP address of the phone making the request in the DeviceListX report, and from the phone name, you have to look up the owner / currently logged in user via AXL/Extension Mobility webservice, and then you access that user's personal directory either by modifying the existing application so that it doesn't do any authentication (since you don't have per user parameters for the directory button url) - the authentication is implicit by looking at which user owns a phone or is currently logged in (the latter in the extension mobility case).
