Create a new Antivirus and Antispyware policy...
Go to file system autoprotect--> Action...
U will find a lock icon in front of dropdown box..
Click on the icon to change the state.
If the icon is in unlock state u can change these setting from clients also.
Then assign this policy to group where u want manual selection.
I don't think any option is there to set this action when a popup comes(i.e. in the popup window).