Hi,

Let me put your requirement in my words
You want to create a group called SOAPS(which includes all soap categerioes) and want to count all the items in that group??
If yes then,

create a formula as
If {Field_name} like "Soap\Soap*" Then "SOAPS" Else {Field_name}

create a group on this formula and write other formula to count all the items in that group
Count({Items},{@Formula})
Or you can use Insert > summary > Select aggregate Count function counting the items in that group.

--Praveen G