Subtotals in TM1 websheets

[RookieTM1]

Hello!

I have a standard websheet on a TM1 cube with write-back functionality (see attached file).

Cost Description and Cost are the input columns part of the same dimension where users can input values through the =DBRW() function.
The other dimensions have subsets created through MDX in the cell containing a TM1RptRow formula:
Department {TM1SORT({TM1FILTERBYLEVEL( {TM1SUBSETALL( [DEPARTMENT] )}, 0)},ASC)}
Supplier {TM1SORT({TM1FILTERBYLEVEL( {TM1SUBSETALL( [SUPPLIER] )}, 0)},ASC)}
Service {TM1SORT({TM1FILTERBYLEVEL( {TM1SUBSETALL( [SERVICE] )}, 0)},ASC)}
Cost type number {TM1SORT({TM1FILTERBYLEVEL( [COST TYPE NUMBER].[SUBSET X], 0)},ASC)}
Description number {TM1FILTERBYLEVEL( {TM1SUBSETALL( [DESCRIPTION NUMBER] )}, 0)}

Is there a way to add two subtotals to the TM1 websheet to sum across the dimensions (displayed subsets) in the table? Can this be achieved through MDX?
I can't make this report in Report Studio since I need the write-back functionality...