Create table based on parameter value

[PKPK90]

Hi, I am trying to create table based on parameter value.

If parameter value is "*AllCustomers" then no filter to the table, but when Parameter value is different then filter by Parameter Value.

DEFINE

if (@customer = "*AllCustomers",

CALCULATETABLE (

 SUMMARIZECOLUMNS ( 'ItemBOMBlowout'[ProdCodeDesc]))

,

CALCULATETABLE (
    SUMMARIZECOLUMNS ( 'ItemBOMBlowout'[ProdCodeDesc]),
    'TotalOrderedByCustomer'[CustomerName] = @customer))

but it does't work, probably the syntax is wrong

[PKPK90]

I also tried this one
DEFINE
var Tabl1_=
        CALCULATETABLE ( SUMMARIZECOLUMNS ( 'ItemBOMBlowout'[ProdCodeDesc] ) )
var Tabl2_=
        CALCULATETABLE (
            SUMMARIZECOLUMNS ( 'ItemBOMBlowout'[ProdCodeDesc] ),
            'TotalOrderedByCustomer'[CustomerName] = @customer
        )
        
      
RETURN 
IF(@customer = "*AllCustomers", Tabl1_, Tabl2_)   

The syntax for RETURN is incorrect