Cannot pass expression on command line

I am trying to pass an expression in on the command line but it is not getting to ssis correctly

dtexec -f "C:\Documents and Settings\simonsa\My Documents\Visual Studio 2005\Projects\Integration Services Project3\Integration Services Project3\Package.dtsx" /set \Package.Variables[User::datevar].Properties[Expression];(DT_DATE)"01 feb 2006"

the "s are getting stripped so that the SSIS is trying to use expression (DT_DATE)01 Feb 2006 which is of course valid.

How can I achieve this, I think its a bug in the way dtexec is parsing the command line.