Do function on only 1 Control of NumericUpDown

Question

I let a supertooltip (from DotNetBar) appear on every control of NumericUpDown. But I only need a supertooltip on the TextBox of NumericUpDown. Here is my current code:

foreach (Control c in NumericUpDown.Controls)
{
    NumericUpDownToolTip.SetSuperTooltip(c, NumericUpDownSuperToolTip);
}

//Declarations:
//NumericUpDownToolTip is a SuperToolTip from DotNetBar
//NumericUpDownSuperToolTip is the configuration of the SuperToolTip (for example: the text of the tooltip)

So how do I set the tooltip only on the textbox?