After much swearing, I found a way to do this. I'm sure it's not the most efficient way to do it, but it works.
I have a view that displays detail records for submitted requests in a repeating table, and each row/record has a small button in the left-most column. I added a query field for my Request ID (the primary key for each of my forms) beneath the table and set its width = 0 px (don't need to/want to see it). The Request ID is also displayed in my repeating table.
In the onClick for each row's button, I set the value of the Request ID query field = the Request ID for that row:
XDocument.DOM.selectSingleNode("//dfs:queryFields/q:Requests/@RequestID").text = _ eventObj.Source.selectSingleNode("@RequestID").text
Still in the onClick, I switch views to my data entry screen:
XDocument.View.SwitchView("Submit Request")
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Now, on that hidden query textbox, I added a rule that says if it's not blank, submit to my main data connection.
That more or less accomplished what I was trying to accomplish -- the end result is that I'm taken to my data entry view, and it's pre-populated with the information from the request.
I still have a problem, though -- the data from the other table in my main data connection still isn't coming in. Argh! Hilary had suggested some things on an old thread of mine. Off to review her suggestions again...