Apth query - range check

Hi all,
I store some data in XML, along with the date it was created. The Datetime.Ticks property has the no; of ticks since the year 1100. I want to allow the users to select a date range and display data for the selected dates to be filtered. I use Ticks to select nodex based on that, it works.
so, //Tasks/task[@Ticks>16588372930411]" works , note that ticks is a long type.

But using ticks to compares does NOT work Like:

//Tasks/task[@Ticks>16588372930411 and @Ticks<83744578232].

Is my xpath query wrong? how do we apply a between x and Y operator here. Iam doing this in C#. Any help would be greatly appreciated. Thank you.

CT.