1) create a query on your dataset
2) in the SELECT/SORT tab, keep all the columns you need at the end
3) in this tab, choose a value in the SIGMA drop-down list (just right to the check boxes) for the variable of which you want to use frequencies
4) drag and drop one more time this particular variable in the SELECT/SORT TAB, and give it a value in the SIGMA list
5) rename this last column COUNT
6) go to the GROUP FILTERS tab, and build a condition using the newly created COUNT variable (should be at the very bottom of the list on the left).