Hierarchy vaiable

HI All,

I have created a hierarchy node variable (zvar) for posting period (0fiscper3).......

posting period is time char and hierarchy is FY Quaterly(quaterly 1, 2, 3, 4) for the same.....

But not able specify offset for ZVAR...right click to specify offset is greyed out......why? please help.....i want to calulate present and previous quaters....

Do i need to write any code?

Please help

Regards

Raj