This created my first External Data recordset, from which I dragged and dropped a single row onto the Visio page to test.
I flipped over into VBA (ALT F11) to interrogate the relevant data recordset properties using the Immediate Window: This revealed that a Select statement is created ?
From the source server attempt to update the bit field over the link.
SQL Server will execute a full remote scan before it does the update. Dan, It appears we jumped the gun when we reported that we have found and checked in a fix for the problem you reported.
The Table Def object ccorresponding to a linked table has a Connect property that contains the connection string to the "real" remote database and a Source Table Name property that contains the name of the table in the remote database. If it's for changing the connection to the database you can use the function Update Linked Table().