Beginner: TRY and CATCH fonctions nothing catches

[mrspock3333]

Hi, I am trying to get TRY and CATCH fonctions to work, but nothing is catching, here is what I have done (note I am new to VB)...

In my textbook I have a sample:

Try
         monthlyInvestmenmt = convert.ToDecimal(txtMonthlyInvestment.Text)
         YearlyInterestRate = Convert.ToDecimal(txtInterestRate.Text)
         years = convert.ToInt32(txtYears.Text)
Catch ex As FormatException
         messageBox.Show("A format exception has occurred. Plse check all _
         entries.")
 
End Try

-----my code below...

Now according to my instructions I must start the debugging to obtain the exception, but nothing will catch using my code, it just goes thru as it was meant to be...???

Try
Catch ex As Exception
    If txtCurrValue.Text = "" Or txtRate.Text = "" Or txtPeriods.Text = "" 
         Then MessageBox.Show("Plse ensure all required field are complete")
         Exit Sub
    End If
    Else
         dblRate = TxtRate.Text
    MessageBox.Show(ex.Message & vbCrLf & vbCrLf & ex.StrackTrace, _
    ex.GetType.ToString)
End Try

-------

When running the code it works fine, do I have to create an error for the code to catch it, and if nothing catches how do I know that the Try Catch functions worked?

I know it is basic, but that process is not clear to me, even after reading about it. Tks for your help.