SSIS in VS2010 - Trying to map an ODBC connection to a package variable -

i'm trying deploy ssis packages in way allows me use variables determine connections use, despite finding fair amount of info on subject nothing seems work. i've setup simple project sql task , odbc connection. parameterized , ended this:

but when use expression property of sql task set connection property connection variable created error:

can little here on i'm doing wrong? thanks.

in nutshell - addressing wrong property.
@ execute sql task have connectionmanager property holds name of connection manager, not connection string itself. thus, ssis reporting cannot locate conn manager name 'dns=ea_stage'. need specify expression on connection manager itself, configuring connectionstring property.
alternative approach task - specifying conn string outside of package @ runtime. can done dtexec parameters directly like described here. if used project deployment model, can pass conn strings witn ssis catalog environments or address dtexec /par switch.