Exp(Log(K) / N)

Private Sub cmdCalculate_Click()
Dim the_root As Double
Dim the_number As Double
Dim the_result As Double

    On Error GoTo CalculateError
    the_root = CDbl(txtRoot.Text)
    the_number = CDbl(txtNumber.Text)
    txtResult.Text = Format$(Exp(Log(the_number) / _
        the_root))
    Exit Sub

CalculateError:
    txtResult.Text = "***"
End Sub