A calc for a subset of dimension members

No, you don't need a for loop for this, you can use build in functionality of the api.data.calculate function.

api.Data.Calculate(formula, accountFilter, flowFilter, originFilter, icFilter, ud1Filter, ud2Filter, ud3Filter, ud4Filter, ud5Filter, ud6Filter, ud7Filter, ud8Filter, onEvalDataBuffer, userState, isDurableCalculatedData)

Every variable in this function, with the exception of the formula one, is optional. You can control with the filter variables the members the calculation will be executed for.

Here are some samples:

UD2: All base members of Top, but not None

api.Data.Calculate("A#Profit = A#Income - A#Expense",,,,,,"U2#Top.Base.Remove(None)")

The UD3 members with text1 attribute = "Calculate" :

api.Data.Calculate("A#Profit = A#Income - A#Expense",,,,,,,"U3#Americas.Base.Where(Text1 = Calculate)")

A comma separated list of UD1 members:

api.Data.Calculate("A#Profit = A#Income - A#Expense",,,,,"UD1#Sales, UD1#None")

You can also use them all together:

api.Data.Calculate("A#Profit = A#Income - A#Expense",,,,,"UD1#Sales, UD1None","U2#Top.Base.Remove(None)","U3#Americas.Base.Where(Text1 = Calculate)")

or combine filters with a comma (inside the quote):

api.Data.Calculate("A#Profit = A#Income - A#Expense",,,,,,"U2#Clubs.Base,U2#Balls.Base")

Even complex filters are supported:

api.Data.Calculate("A#Profit = A#Income - A#Expense",,,,,,,"U3#Americas.Children.Where(Text1 = Calculate).base.remove(None)")

This feature of api.data.calculate should eliminate the need for for loops to a minimum.