adding irish (GMT) timezone to TimeZone.TIMEZONE_ID

Using asp.net/vb.net 2005 

I have a switch statement that needs to include GMT (Greenwich Mean Time) for a location that we have in Ireland.

I am in the US and the timezones included in the switch stmt below are all US times and does not allow me to include irish time:

 ex:  i also want to include a case in the code below that is something like

TimeZone.TIMEZONE_ID.GMT

but i cant do that, intellisense only allows me to use the US times.  I assume that I have to use Culture object for this? 

please help and include any code samples.

<CODE>
Select Case tz
Case TimeZone.TIMEZONE_ID.EASTERN
Return DateAdd(DateI ...