Dynamic Chart based on Date drop down list

Howdy,

Seems I'm going in circles. Trying to make a chart that's dynamic based on the selection of a drop down list (highlighted in yellow). The chart should show 12 months worth of data based on the selection from the drop down list.

Below are the list of defined names for Chart.

Range =OFFSET(Sheet1!$A$1,COUNTA(Sheet1!$A:$A)-1,0,-MIN(12,COUNTA(Sheet1!$A:$A)-1),1)
North =OFFSET(Range,0,1)
South =OFFSET(Range,0,2)
West =OFFSET(Range,0,3)

Can't seem to work out how to reference the drop down list conditional to the 12 months.

Any help is appreciated. Have attached excel sheet.

http://chandoo.org/wp/2011/04/27/upd...-filter-macro/

this should help you figure it out