1. Create a web service that returns data in xml format.
2. Open SharePoint Designer, Click on "Data View" on the top tool bar. In the side panel that opens click "Manage Data Sources".
3. Click "Connect to a web service..."
4. Data Source Properties -> Fill in values
**Parameters -> Check "The value of this parameter can be set via a web part connection" and insert a default value. (if you don't add a default value then it won't hold the check mark value)
To Use Parameters From/To Another Web Part:
Drag/drop xml web service onto page. This creates a grid view. Click on it. Click the arrow on the top right corner fo the web service grid on page.
Select Parameters link -> "Data View Parameters" window pops up -> Make sure "None" is selected
Web Part Connections -> Get Parameters From -> Connect to a Web Prt on this Page -> Current User Filter & Send Filter Values To -> Cntrl Click on listed items in both sides -> Finish
**Web Services that pull from Sharepoint lists have to be run on sharepoint server.