I have a MDIparent form with a panel inside. Now I had already call a childform_No1 into the panel. But some how I need to call another childform_No2 from childform_No1 to the panel in MDIparent. How can it be? Kindly help! thank.

Can you show us what you have done so far........

how I need to call another childform_No2 from childform_No1 to the panel in MDIparent.

....
            Form a = new Form();
            a.MdiParent = mdiObj;
            a.Parent = mdiObj.panel1;
            a.Show();
.....

My work as show below :
Inside the ParentForm, I have a button with the following code

private void button_Click(object sender, EventArgs e)
        {
            Form1 child = new Form1();
            child.TopLevel = false;
            child.Dock = DockStyle.Fill;
            panel1.Controls.Add(child);
            child.Show();
        }

After that inside the form1, also contain a button that use to call out form2 and allocated at the panel1 of the parentFrom.
I have try to declare the modifier of the panel1 as public, and using the code above to call out the form but some how it can't work also. Any Idea?