Locking window size

Question

Hi,

(All work done in Visual Studio 2008) I've created a parent window for a application I want to create, and it has several buttons up the top of the application window.

The code behind the buttons (just 1 for example) is something like;

            Form2 frmchild = new Form2();
            frmchild.MdiParent = this;
            frmchild.Show();

Now this will open within the parent application.  The problem is, I want to be able to lock the child window to the parent window size minus X ammount from the top of the application to allow spacing for my buttons.

What would I need to do to be able to lock the child window size to the parent window, but I want this to make no difference on the resolution/size the clients are using. 

I don't know it might be easier if I just lock the parent window size so it can't be changed?

Thanks in advance for nay help.