I had the same problem with performance on my mover form when using the AddItem method. It took more code, but I found that if I loaded the items into an array and then used the array as the rowsource for the listbox, the performance was great. To accomplish deleting elements from one listbox and adding them to the other, I used the listbox's listitemid as my array index and manipulated the arrays for each listbox. To keep things neat, I add a property to hold the array on to each listbox. You'll need to sort the arrays in code rather than using the listbox's sort property. Hope this helps.

Regards.

Joel