well im basicly a noob too visual basic .NET and i need some help with this i wanted to try to make a text converter
this is what i have so far

Code:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click 

   textBox2.Text = ConvertMe(textBox1.Text) 

End Sub 

Function ConvertMe(ByVal textData as String) as String 

   Dim tempChar as String ' holds a character to compare to 
   Dim textConversion as String 'holds the converted text 
   textConversion = "" ' initialize empty string VB may already do this i don't know. 

   tempChar = textConversion.SubString(0,1) ' get the first char in the string 
    
   if tempChar = "a" Then 
      textConversion+= "4" 
   End If 
    
    return textConversion 
End Function
but i cant seem to get it to work, ne help would be very nice