OK. I figured it out. The code I was using to replace the connection string in the report file was wrong. Once I fixed that it's working fine.
I can't find much out there on using ReportMax, so just in case someone else is wondering about this, here's the scoop.
Before running a report, if I want to query from a different database (or change the SQL for a report for that matter), I just call this sub with the report file, the target string, and the replacement string.
Private Sub ReplaceTextInFile(WhichFile As String, WhichTarget As String, WhichReplacementText As String)
Dim MyText As String = File.ReadAllText(WhichFile)
MyText = Replace(MyText, WhichTarget, WhichReplacementText)
System.IO.File.Delete(WhichFile)
File.WriteAllText(WhichFile, MyText)
End Sub
I call it like this:
ReplaceTextInFile("C:\Users\Daddio68\Desktop\ReportMax1.rpm", "C:\Users\Daddio68\Desktop\DBOld.mdb", "C:\Users\Daddio68\Desktop\DBNew.mdb")
frmReportTest.ShowDialog()