You are most of the way there. I recommend though that the destination DB NOT be included in the command, set the destination database in your destination connection.
I have uploaded a package that illustrates how this can be done.https://dl.dropboxusercontent.com/u/85082194/SSC/Package-1477191-364-1.dtsx
I have also attached it here in this post..
First I have setup these variables:
I am using expressions to build two commands, one to build the work table and the other to truncate it. The are fed from the variable DestinationTable.
They are then used in the Exec SQL Tasks as such:
We then go to the Data Flow Task, you will notice that I am using an OLEDB Source, this is just to make the demo easier.
The Source just gives 5 rows of data:
The Destination is a setup a little different:
You'll notice the Data Access Mode and the variable. Because the Destination table has an Identity for Field1 the Keep Identity is checked.
This gets us most of the way, you probably noticed the DestinationDatabase variable, that is used to set the catalog at the destination. There are several ways to do this, you can set the whole connection string at run time or a couple other ways. I'm keeping it really simple.
You'll notice the little formula symbol next to the Connection name, I have configured an expression to set the catalog (database) name.
I hope this sheds some light on the situation for you.