Pivot table formula to work out year on year performance Like for Like

[Alpacino]

I have this type of information in a table. put into a pivot table.
Is there a way of using pivot table formulas to work out LFL perofrmance
formula would be ((this year-Last Year)/Last Year)

Anyway of doing this please??

[TABLE="width: 361"]
<tbody>[TR]
[TD="align: center"]Year[/TD]
[TD="align: center"]Wk No[/TD]
[TD="align: center"]YrWk[/TD]
[TD="align: center"]Sales Manager[/TD]
[TD="align: center"]Sales $$[/TD]
[/TR]
[TR]
[TD="align: center"]2011[/TD]
[TD="align: center"]1[/TD]
[TD="align: center"]201101[/TD]
[TD="align: center"]Steve[/TD]
[TD="align: center"]2,476.05[/TD]
[/TR]
[TR]
[TD="align: center"]2011[/TD]
[TD="align: center"]2[/TD]
[TD="align: center"]201102[/TD]
[TD="align: center"]Matt[/TD]
[TD="align: center"]665.29[/TD]
[/TR]
[TR]
[TD="align: center"]2011[/TD]
[TD="align: center"]3[/TD]
[TD="align: center"]201103[/TD]
[TD="align: center"]Sue[/TD]
[TD="align: center"]7,374.54[/TD]
[/TR]
[TR]
[TD="align: center"]2012[/TD]
[TD="align: center"]1[/TD]
[TD="align: center"]201201[/TD]
[TD="align: center"]Steve[/TD]
[TD="align: center"]4,483.00[/TD]
[/TR]
[TR]
[TD="align: center"]2012[/TD]
[TD="align: center"]2[/TD]
[TD="align: center"]201202[/TD]
[TD="align: center"]Matt[/TD]
[TD="align: center"]732.49[/TD]
[/TR]
[TR]
[TD="align: center"]2012[/TD]
[TD="align: center"]3[/TD]
[TD="align: center"]201203[/TD]
[TD="align: center"]Sue[/TD]
[TD="align: center"]6,186.23[/TD]
[/TR]
</tbody><colgroup><col><col span="2"><col><col></colgroup>[/TABLE]