1) Obtain a set of pages:

Pages1Set = {{#ask:[[Category::Category1]] [[MyProperty::P1]]}}

2) Obtain a second set of pages that depend of the first:

for all elements of PagesSet

Pages2Set = {{#ask:[[Category::Category2]] [[MyProperty2::Page1Set(index).pageName]]}}

Page2SetTotal = Page2SetTotal + Pages2Set

3) Display the results in some table

I bet the syntax could be something like below, but this doesn't work:

{{#ask:[[Category::Category2]] [[MyProperty2::{{#ask:[[Category::Category1]] [[MyProperty::P1]]}}]]}}

-James