private void inventoryBttn_Click(object sender, EventArgs e)
{
if (inventoryform == null)
{
inventoryform = new inventoryFrm();
inventoryform.FormClosed += inventoryform_FormClosed;
}
inventoryform.Show(this);
Hide();
}
void inventoryform_FormClosed(object sender, FormClosedEventArgs e)
{
inventoryform = null;
Show();
}