Hi all,
I'm a first year student and in my third week of tutorial work I've hit a landmine and after spending hours on it, I just can't seem to get around why I am getting this error now.

Before I added the 'Msgbox' function, it worked fine however since adding it and executing a function on my form, the system crashes and produces the following error 'Conversion from string "" to type 'Double' is not valid.' near my 'dInitial = CDbl(txtInitial.Text)' line of coding.

This is my coding below

Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click

'calculates the required Payments e.g. Monthly, Yearly and Total'

Dim dInitial As Double
Dim dMonthPay As Double
Dim dYearlyPayment As Double
Dim dTotalPayment As Double

If txtInitial.Text <> "" Or txtLengthOfLoan.Text <> "" Or txtInterestRate.Text <> "" Then
Else
MsgBox("No data entered, please enter data")
txtInitial.Focus()
End If

dInitial = CDbl(txtInitial.Text)
dMonthPay = (CDbl(txtInitial.Text) * (CDbl(txtInterestRate.Text) / 100) / 12)
lblMnthPay.Text = FormatNumber(dMonthPay + (txtInitial.Text / txtLengthOfLoan.Text / 12))

dInitial = CDbl(txtInitial.Text)
dYearlyPayment = (lblMnthPay.Text * 12)
lblYrPay.Text = dYearlyPayment

dInitial = CDbl(txtInitial.Text)
dTotalPayment = (lblMnthPay.Text * 12 * txtLengthOfLoan.Text)
lblTotPay.Text = dTotalPayment

End Sub

Help on this would be greatly appreciated.
Thank you