Gross Amount calculation in different year

[AH]

I have Gross amount calculation different for pror to 2015 and in 2015. The filtering should be based on invoice year.

The Calculation i have in 2015 is:
=num(num(Sum({<SalesType = {'SalesRegister', 'FreeText', 'Service'}>}LineAmount),'##,##0')-(

num(Sum({<GLAccount={101100,115100,115110,115120,225430,420020},SalesType={'FreeText'}>}LineAmount),'##,##0') + num(Sum({<ItemId={'GW_CLX','GW_XTS','CR_L','CR_U'}, SalesType={'SalesRegister'}>}LineAmount),'##,##0')) ,'##,##0')

And Prior to 2015 is:
=num(num(Sum({<SalesType = {'SalesRegister', 'FreeText', 'Service'}>}LineAmount),'##,##0')-

num(Sum({<GLAccount={101100,115100,115110,115120,225430,420020},SalesType={'FreeText'}>}LineAmount),'##,##0'),'##,##0')

How to i put the Invoice year in these two piece of expression that will show me the gross amount Prior to 2015 and In 2015 only?

I appreciate your help.

Thanks,

Shan