I Am fully agree with Bruce.
We are also havinf same issue.
Even when we try to copy paste few values separated by semicolon its not working, The WEBI document error out saying the values doesn't exist.
Being a market leader in reporting tools , this is a simple featuer most of teh users wants like copy paste multiple descrete values of PO , SO , Articles etc..
Please share if anyone has any otehr workwround....... with WEBI on BEx.