Report Viewer – Setting the decimal places for a textbox value

Lisa Nicholls gives a complete answer in this thread about dynamically defining a report. You'll want to scroll down some before you get to a useful answer. This thread most directly answers your question about controlling which columns are displayed.

These same techniques can be used to size the columns programmatically, but your code will have to figure out the appropriate column widths.

Try calling ReportViewer.Reset() prior to loading the new report file.

I currently doing exactly this in my ReportViewer control, however, the source code is at work. If the Reset does not work, I will post my code here on Monday morning. It can definitely be done.