VS 2008 - Read Value From Config File

I have code that reads a value from a config file (not web.config) given a key. It looks like this:

Code:
Public Shared Function GetCustomConfig(ByVal ValuetoGet As String, ByVal ConfigFileValue As String) As String
Dim Returnvalue As String = String.Empty
LoadConfig(ConfigFileValue)
For Each KeyValue As String In AppSettings.Keys
If KeyValue = ValuetoGet Then
Returnvalue = AppSettings.Item(KeyValue).ToString
End If
Next

Return Returnvalue
End Function

So if my config file which is named my.config has this entry: <add key="TempArea" value="c:Temp"/>I would call GetCustomerConfig("TempArea", "my.config") and the function would return "c:Temp". Most of the time this is what happens. But sometimes I get an exception: Collection was modified after the enumerator was instantiated.

Is there a better way to get the value given the key? This is code written long ago by my predecessor, and I am not sure I want to use it anymore. If I do use it, I will have to do something so that it is more reliable.