Substruction of listbox data

[#1]

Hi,

Consider a case of 2 listboxes;

1st listbox has data 'April' and 'June'

When April is chosen 10 items are being selected and when it is June 12 items are being selected in the 2nd listbox

I want to show the differential 2 items in the 3rd listbox.

How can I achieve that without touching the query?

Thanks

[Gysbert_Wassenaar]

See this discussion

[#3]

Thanks for your reply.

In that example, the expression intersects 2 different listboxes. I have only 1. Do I need to -duplicate- the listbox (using resident?)? Is there any simpler way without duplicating?

Thanks!

[Gysbert_Wassenaar]

See attached example.

[#5]

I have tried with the attached document.

I could not understand the expression but ur sample works fine. In your example you have 2 items in your month listbox, so they basically intersects with the other item.

I have more than 2 items in the month listbox so when I tried the exact same expression it did not work for me. How should I change the expression so that interesection is done between the selected item and the previous one.

Thanks a lot!

[#6]

Considering a listbox with more than 2 items, is it possible to change the expression so that intersection is done between the selected item and the previous item of the selected.

For ex: There are months in the listbox(but consider them as text data not real dates), when I choose June I want the 2nd listbox intersects with the May's data. If it February is selected, it should intersect with January's data.

Thanks!