You would put that on any event that you want to trigger the Sub form to be either visible or hidden. When you able to have a look at the sample I posted earlier you will see I have the code in the On Current event as well as the buttons On Click event.
Book mark this link for a handy reference for the correct syntax for addressing subforms, their properties and controls.
so theoretically... i insert my subform. go into the properties of that subform and change the visible to no (would this work the same as inserting the visible=false). then in the double click event of the list box, i insert the visible=true part?
something odd... i am getting an "Enter Parameter Value: Forms!FRM_SearchMulti!SrchText" error. not everytime but sometimes i do. defenitely every time i open the query.
I'm guessing that this will be happening when the form FRM_SearchMulti is not open or open in design view. As the query is drawing criteria from this form it will ask you to "Enter Parameter Value:" when it is unable to get it from the form.