Distinctcount records in fact table not exist in dimension table.

[AnSchmi]

dear communitiy,
I have in my dimension table orders not matching orders in fact table and I would like to show them in a table.
The Relationship is by Order.No. 
I'm trying to calculate the distinct number of orders in fact table not matching the orders in dimension table. 
No of orders with missing order detail records = 

CALCULATE(

    [No of Work Order Header],

    FILTER(

        'd Tbl Items Production Header',

        'd Tbl Items Production Header'[Work.Order.No] not exist in fact table 'f Tbl Items Production Details'[Work.Order.No] 

    )

    )
Can anyone help to understand the logic. 
Thanks a lot 

Andreas

[johnt75]

Try

No of orders with missing order detail records =
CALCULATE (
    [No of Work Order Header],
    FILTER (
        'd Tbl Items Production Header',
        ISBLANK ( RELATED ( 'f Tbl Items Production Details'[Work.Order.No] ) )
    )
)

[AnSchmi]

Dear johnt75, 
unfortunately this is not working due to following error
The column 'f_Tbl_Items_Production_Details[Work.Order.No]' either doesn't exist or doesn't have a relationship to any table available in the current context. 
There is a link to a very limited extract of my model.
https://fileshare.ssl.iscar.com/data/public/8afb8a 
Would you pls. have a look again on it.
Thanks a lot
Andreas