>before report all table is there.... and also after report...

which is why I suspect that the expression is not accessing the table, but a different one. Maybe a typo in the alias name in an IIF condition or as the second part of an AND clause.

> But, Never ask for OPEN tables..

But it does prompt for a table when you preview, doesn't it? So, if you pick a table in the dialog, do you get any other error?