SQL Help: Conditional Statement Using Inserted

I'm learning SQL and here I'm trying to use two things that I'm not familiar with - IF statements and the Inserted temporary table.

Here's the background - skip this paragraph if you like. I'm working on a tasking system for the Help Desk - they get requests from the web site for various items and I break up the request into Software, Hardware, Accounts, etc tables and list the status of each item as "Requested". I'm also keeping a Tasks table to make work orders for each item requested. I've got triggers on the Accounts and Hardware tables that automatically make a new task for those items but the Software is more tricky because all software for a given request should be just one task. Software installs are all done by one person at the same time.

So I'm trying to make a trigger that creates a new Task when a new Software record is inserted. But if a task already exists with the same RequestID (meaning they requested two peices of software and this is the second one), then I just want to update the task already created. Here's what I got:

 1 CREATE TRIGGER [NewSoftwareTask]
2 ON [dbo].[Software]
3 AFTER INSERT
4 AS
5 BEGIN
6
7 -- If a software task already exists for this request
8 -- then update it. Otherwise create a new task.
9
10 if exists(select TasksID
11 from Tasks
12 where Tasks.RequestsID = inserted.RequestsID and
13 TasksType = 'Software')
14 BEGIN
15 UPDATE [BGHelpdesk].[dbo].[Tasks]
16 SET [TasksDescription] = [TasksDescription] + vbcrlf + "Install " + inserted.SoftwareType + ". " + inserted.SoftwareComments
17 WHERE Tasks.RequestsID = inserted.RequestsID and
18 TasksType = 'Software'
19 END
20
21 else
22
23 BEGIN
24 INSERT INTO [BGHelpdesk].[dbo].[Tasks]
25 ([RequestsID]
26 ,[TasksType]
27 ,[TasksSubType]
28 ,[TasksTitle]
29 ,[TasksDescription])
30 SELECT
31 s.RequestsID
32 ,'Software'
33 ,s.SoftwareType
34 ,'New ' + s.SoftwareType + ' Account for Request ' + cast(s.RequestsID AS varchar)
35 ,s.SoftwareComments
36 FROM Software s join
37 inserted ON s.SoftwareID = inserted.SoftwareID
38 END
39 END
40 GO


It keeps balking at lines 12 and 17 saying "The multi-part identifier "inserted.RequestsID" could not be bound." The ELSE statement is what I use on the other tables and it works fine so the inserted temp record seems pretty straightforward but I must be doing something wrong...