Hi,

This might get you started...

using System.Windows.Forms;

class Parent : Form
{
    private Child childRef;

    private void menuProperties_Click(object sender, EventArgs e)
    {
        if(childRef == null)
            childRef = new Child(this);

        // get whatever item is selected
        // itemReference = myListBox.SelectedItem

        childRef.Show();
        childRef.ShowProperties(itemReference);
    }

    public void NewItem(bool down)
    {
        if(down)
            // set next item in the list as selected
        else
            // set previous item in the list as selected

        // get the selected item
        // itemReference = myListBox.SelectedItem
        childRef.ShowProperties(itemReference);
    }
}

class Child : Form
{
    private Parent p;

    public Child(Parent p)
    {
        this.p = p;
    }

    private void DownButton_Click(object sender, EventArgs e)
    {
        p.NewItem(true);
    }

    private void UpButton_Click(object sender, EventArgs e)
    {
        p.NewItem(false);
    }

    public void ShowProperties(Item i)
    {
        // get properties for i and display them
    }

}