How to calculate average over a subset of all

[MarkusBohse]

I'm having three tabels like this:
Employee (EmpID, name, EmployeeAge, companyID,...)

Comapny (CompanyID, Name, RegionID)
Region (RegionID, Name)

What I need is a calculation of the average EmployeeAge for the selected company, the whole region and overall.
The first one is easy and so is the last one using the ALL function. But I'm struggling to get the average for the region of the selected company.
I had a look at ALLEXCEPT, but so far I cannot get to return the correct result.
Any hints are appreciated

[Anonymous]

-- If the structure is:
-- Employee[CompanyID] * : 1 Company[CompanyID]
-- Company[RegionID] * : 1 Region[RegionID],
-- then:

[Avg Employee Age] = AVERAGE( Employee[EmployeeAge] )

-- This measure calculates the average age
-- of all employees that work in companies
-- that belong to regions that are visible
-- in the current context. For instance,
-- if one employee has been selected, then
-- it'll return the average age for the
-- region to which the company of the employee
-- belongs.

[Avg Age for Regions] =
var __visibleRegions =
	SUMMARIZE(
		Employee,
		Region[RegionId]
	)
var __avgForVisibleRegions =
	CALCULATE(
		[Avg Employee Age],
		ALL( Company ),
		__visibleRegions
	)
return
	__avgForVisibleRegions

This measure honors all the filters that have been put on the Empolyee table itself.

Best

Darek