Query Filter Function?

when I make a report, I want it to chose the date in "Query Filters` place. this option is going to be between and i am going to chose one of them by myself and the other is going to be chosen 4 months before which I chose. for example, I chose june as a filter, it should give me the february automatically based on my function. this kind of function can be written filter which is in "Query Filters"?????? whenever I write =currentMonth() in filter place, It brings up the data based on the last month.