variables in SSIS

Hello
I haven't found any solution neigther on MSDN Website nor Books online
so decided to ask a question to real experts :-)

I'm quite new to SSIS and VS so the aswer might be obvious but not for
me.

In the first step of Data Flow I want to select records from the
table.
I use OLE DB Source and in Data access mode i select SQL cemmand.
Is it possible to user variables (created on package) in WHERE clause?

I get error ...
Any ideas?

Thanks for any suggestions.
Pawel