set analysis with variable

[#1]

I want to use varaible in analysis

for example

SYear and SMonth are variables.

The below expression work well

count(total<UsageYearMonth>{<UsageCategory = {'ActiveStudent'},

UsageYear = {'$(=SYear)'},UsageMonth ={'$(=SMonth)'}>} distinct OrderId)

But if I want to  use function on the varaible ,how should I write the set analysis?

I mean if now I have a varaible named ReportDate,date type

I want to use Year function to get the year part. like Year($(=ReportDate))

then the analysis should be

count(total<UsageYearMonth>{<UsageCategory = {'ActiveStudent'},

UsageYear = {'Year($(=ReportDate))'},UsageMonth ={'Month($(=ReportDate))'}>} distinct OrderId)

I dont know how could i get it work?

[#2]

Than you for so detailed description,but it seems not right.

And I've figured out the right way.

It should be below:

count(total<UsageYearMonth>{<UsageCategory = {'ActiveStudent'},

UsageYear = {$(=Year('$(ThisMonthEndDateVar)'))},

UsageMonth = {$(=Month('$(ThisMonthEndDateVar)'))}>} distinct OrderId)