Add totals within a specific data structure inside RDLC Report

Hi everybody,

I have one specific problem that I can not solve. My data set (Detail Tablix) inside RDLC report has the following structure:

On that structure I need to insert SubTotals (for column Amount) for each level of data as shown in the following picture:

So, we have five different levels that we need to calculate Totals (to a depth of 3): Level 1, Level 1.1, Level 1.2, Level 1.2.1, Level 1.2.2

For each Level there is an indicator inside the column LineNo which marks the beginning and end of the group: GB - Group Begin, GE - Group End

Do you have any idea or tips how to achieve that? Just to mention, this is the input data set to RDLC and is not subject to any manipulation at the level of the database.

I really appreciate your help. Thanks.