EVALUATE
TOPN (
    20,
    FILTER (
        CALCULATETABLE (
            SUMMARIZE (
                'Customer',
                'Customer'[Name],
                'Customer'[CustomerId],
                "Sales per Sqft", 'Sales'[Sales per Sqft]
            ),
            DATESBETWEEN (
                'Dates'[Date],
                DATE ( 2011, 4, 1 ),
                DATE ( 2012, 4, 30 )
            ),
            ( 'Property'[PropertyId] = 108
                || 'Property'[PropertyId] = 27
                || 'Property'[PropertyId] = 138
                || 'Property'[PropertyId] = 1
                || 'Property'[PropertyId] = 120
                || 'Property'[PropertyId] = 28
                || 'Property'[PropertyId] = 57
                || 'Property'[PropertyId] = 137
                || 'Property'[PropertyId] = 50
                || 'Property'[PropertyId] = 139
                || 'Property'[PropertyId] = 39
                || 'Property'[PropertyId] = 122
                || 'Property'[PropertyId] = 126
                || 'Property'[PropertyId] = 2 )
        ),
        NOT ISBLANK ( [Sales per Sqft] )
    ),
    [Sales per Sqft],
    0,
    'Property'[Property Name],
    0
)
ORDER BY [Sales per Sqft] DESC, 'Customer'[Name] ASC