Try

CREATE FUNCTION CaseResourceCost  (@meetID int)
RETURNS decimal(12,2) AS
BEGIN
        Declare @returnValue decimal(12,2)
        select @returnValue = isnull(sum(cocasedata.itemunitcost * coCaseData.ActualQty),0) as avgResCost
	FROM dbo.meetings  INNER JOIN
	             dbo.meetproc  ON meetings.meetingnumber =meetproc.meetingnumber INNER JOIN
	             dbo.cocasedata ON meetings.meetingnumber = dbo.cocasedata.meetingnumber
	             where meetings.meetingnumber = @MeetID

      return (@returnValue)
END

>Can I create a udf function that performs a query, that returns a single row with a single field, and then return the value of the single column/record?
>
>Here is what I have tried:
>

>CREATE FUNCTION CaseResourceCost  (@meetID int)
>RETURNS decimal(12,2) AS
>BEGIN
>        Declare @returnValue decimal(12,2)
>        select isnull(sum(cocasedata.itemunitcost * coCaseData.ActualQty),0) as avgResCost
>	FROM dbo.meetings  INNER JOIN
>	             dbo.meetproc  ON meetings.meetingnumber =meetproc.meetingnumber INNER JOIN
>	             dbo.cocasedata ON meetings.meetingnumber = dbo.cocasedata.meetingnumber
>	             where meetings.meetingnumber = @MeetID
>
>      set @returnValue= avgResCost
>      return (@returnValue)
>END
>

>
>But I get the following error
>---------------------------
>Microsoft SQL-DMO (ODBC SQLState: 42S22)
>---------------------------
>Error 207: Invalid column name 'avgResCost'.
>Select statements included within a function cannot return data to a client.
>---------------------------
>OK
>---------------------------