Set analysis issue

[risabhroy_03]

I am using the below expression but quantity is coming 0.

if([Table Source]='WHUIL200',Sum({$<("Invoice_Date_GMT")={'$(vLastmonthdate)'}>} Quantity))

Basically, my date field ("Invoice_Date_GMT") should match my variable vLastmonthdate.

[rwunderlich]

I don't think the () around the "Invoice_Date_GMT" are valid.

-Rob