How do I rotate a selected group of objects by an exact value?

[Jaycerulz 1]

Hey guys, Been trying to figure this out (late at night, so real tired too).

I can select a group of walls and rotate them with shift but I want them to be at exactly 90 deg to some other walls. I know you can go into each individual wall and make it 90 deg but I was wondering if there is a way you can just select a bunch of stuff and rotate it by an exact amount (and not just guess).

The reason it needs to be exact is because I have a bunch of long walls. If it is slightly off 90 deg the other end is way out alignment at the other end.

Thanks for any help / discussion.

[RegEdit 10]

Did you mean this?

_walls = [wall1,wall2,wall3];
{
   _x setDir 90;
}
forEach _walls;

[Jaycerulz 1]

Would that mean if I had 15 walls I would have to name them all? I also mean as a group. Like this -> http://i.imgur.com/vqpYsgl.jpg