manipulate margins

[Carsten Grewe]

Hi!

I try to manipulate the margins, but couldn't do it until now. I use the 
report class. In Layout-Document-Paper, Papersize is A4, Special is none and 
the geometry package is used. As far as I got the User's Guide I should be 
able to adjust the margins now, but whatever figures I put in the fields, I 
can't click on OK. Why is that?

As an alternative: Is there a command for the Latex preamble to set the left 
margin to 3 cm? Would be great!

Thanks
Carsten