How can Field Parameters be used in DAX measures?

[speedramps]

Can a Field Parameter DAX expert help me please.

How can Field Parameters be used in DAX measures?

Click here to download example PBIX from Onedrive 

In the attached PBIX I have crated a fictional example for a pet shop
There is a Field Parameter for types (Vet, Pet type and Colour)

and Field Parameter for metrics (Cost, Sales, Profit and Tax)

The green card = the field parameter “Metrics[Metrics Value]”.

The Row count = the number of rows.

I want the bottom card to show the average but the DAX syntax won’t allow the Field Parameter highlighted in red

Average =
DIVIDE(
Metrics[Metrics Value],[Row count)

Please can you suggest a method of calculating the average of the Field Parameter without creating a separate formula for cost, sales, profit and tax. 

Please create an working example by downloading the above attached PBIX.

Thank you.

[DataInsights]

@speedramps,

Try this measure:

Average = 
VAR vSelectedMetric =
    SWITCH (
        MAX ( Metrics[Metrics Value] ),
        "Costs", [Costs],
        "Sales", [Sales],
        "Profit", [Profit],
        "Tax", [Tax]
    )
VAR vResult =
    DIVIDE ( vSelectedMetric, [Row count] )
RETURN
    vResult

[speedramps]

Thank you very much for replying and going to the effort of writing a DAX script.

Your answer is a work arround.

However, it does not answer the question how to reference Field Paraneters in DAX measures.

Does anyone know the answer please?