Do you know the name of the Page in question ? Or do you need a 'relative' address here (like '..' in Filesystems or SLT ?) - if the former - you should be able to use an absolute expression like 'Content_1.CustomerPage'; but if you don't know the name, then I'm stuck (I can't find a way of getting a 'relative' address to work here....)
Provided Content_1 is indeed the named top level page. You can also use "Content_1.CustomerPage".
Basic principle is this,
Whenever you are within the section context, the page in which the section is rendered will be the Primary page for that section. so all the properties inside the section starting with dot will be deferenced in that context (i.e. Primary.propertyname). Now to refer a property from the named page, you can always use absolute reference like ToplevelPage.page1