How to create script logic based on number of time periods

Hi,

We have below requirement to create script logic based on number of time periods

We are going to run the script for the below selection

Category = PLAN

Planyear = 2016

Time = 2016.02 to 2017.07 (18months) as feb is the current month we are going to run from current time period

The account WM_FT_GROSS_RATE should be same as WM_FT_GROSS_AMT for the first 12 months forecasting and from 13th to 18th month it should be WM_FT_GROSS_RATE /12

So,

*XDIM_MEMBERSET ACCOUNT = WM_FT_GROSS_RATE

*XDIM_MEMBERSET TIME = %TIME_SET%

Considering above requirement, who to execute first WHEN condition to all time members from 2016.02 to 2017.01 and second WHEN condition for the time periods 2017.02 to 2017.07.

*WHEN ACCOUNT

*IS WM_FT_GROSS_RATE

*REC(FACTOR=1, ACCOUNT = WM_FT_GROSS_AMT)

*ENDWHEN

*WHEN ACCOUNT

*IS WM_FT_GROSS_RATE

*REC(EXPRESSION=%VALUE%/12, ACCOUNT = WM_FT_GROSS_AMT)

*ENDWHEN