VS 2010 Methods

Hi all

First post and very new to VB.
Trying to finish the construction of a method (design code) before it is implemented in VB.
The method should removes all non-letter characters from an input string and convert the remaining characters to lower case.
Anyone able to help?

thanks


Method Casechange(input As String) As String
’Preconditions: none
’Postconditions: A string is returned consisting of all the letter
’characters from input in the same order and with the same
’multiplicity, but in lower case. Example, input is
’"Happy Birthday!", then "happybirthday" is returned.

result As String
hold As Char
Set result To ""
For i As Integer From 0 To ’Add expression here.
’The loop body goes here, the For loop should add all the letter
’characters in input to result.
End For
’The line of code to convert result to lower case goes here.
Return result
EndMethod