programmatically collapse or expand selected groups in reporting services

I need to write a report that on startup shows specific groups expanded while other remains collapsed. I've been searching for a property lik开发者_如何转开发e "collapsed" or "expanded" or similar at the group level, but I found none.

The only way I've found to do something similar is through the "hidden" properties of the detail. But this way the +/- mark to the side of the group works in the opposite way: it shows '-' when the group is collapsed and '+' when it is expanded.

Is there a better way to expand or collapse a group based on a programmed condition?

To solve the +/- mark problem, go to the Properties of the Element which contains the +/- symbol, and set the property "InitialToggleState" using an expression.