Is there a way to pass through a person's credentials when using a control like "Query Excel Services"?
Whenever I use the "Query Excel Services" control, I have to put in my own login ID and Password for the control to work. Which then means I have to go back into the workflow every quarter and change my password when my company mandates I do so. Is it possible to have a user's credentials pass through this kind of control?

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colin_e commented
This is a critical requirement in a typical enterprise environment. I am bascially prevented from using any of the web service based actions (Call Web Service, Query Excel Services etc.) because they require hard-coded login credentials.
Hard-coding passwords is really bad practice in general.
Further, just like the OP our IT policies mandate password changes every 90 days. Having a workflow set up that's guaranteed to fail every 90 days unless someone goes in and edits the code is a recipe for disaster. What happens when the guy that wrote the workflow leaves the oganisation for example?