INSERT INTO Using Stored Procedures

Hi,
I'm trying to insert some values into 2 tables using stored
procedures (which should be pretty straight forward) but I'm running
into problems.
Given below are my 2 sp that I'm using:
 

 USE [DBName]
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO


CREATE PROCEDURE [dbo].[AddToProject] (@DeptCode varchar(20), @ProjectTitle varchar(300), @ProjectDetails varchar(3000), @ProjectManagerID int, @RequestedBy varchar(100), @DateRequested datetime, @DueDate datetime, @ProjectStatusID int)
AS
BEGIN TRANSACTION
SET NOCOUNT ON

DECLARE @Dept varchar(50), @ProjID varchar(50)

SET @Dept = REPLACE(CONVERT(char,@DeptCode),'.','')

EXEC ('INSERT INTO dbo.tbl_ProjectNumber' + @Dept + '(DeptCode) VALUES(' + @Dept + ')')

EXEC GetProjID @Dept, @ProjID OUTPUT


INSERT INTO dbo.tbl_Project (ProjID, ProjectTitle, ProjectDetails, ProjectManagerID, RequestedBy, DateRequested, DueDate, ProjectStatusID)
VALUES (@ProjID, @ProjectTitle, @ProjectDetails, @ProjectManagerID, @RequestedBy, @DateRequested, @DueDate, @ProjectStatusID);


COMMIT TRANSACTION

---------------------------------------------------------------------


USE [DBName]
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO


CREATE PROCEDURE [dbo].[GetProjID] (@DeptCode varchar(20), @ProjID varchar(50) OUTPUT)
AS
BEGIN
SET NOCOUNT ON

DECLARE @ProjectNumber varchar(100), @Table varchar(100)
SET @ProjectNumber = 'ProjectNumber' + REPLACE(CONVERT(char,@DeptCode),'.','')
SET @Table = 'dbo.tbl_ProjectNumber' + REPLACE(CONVERT(char,@DeptCode),'.','')
EXEC ( 'SELECT @ProjID = MAX('+@ProjectNumber + ') FROM ' + @Table )

SET @ProjID = @ProjID + '-' + @DeptCode

END
 
When I run the AddToProject sp using the following values:
 USE [DBName]
GO

DECLARE@return_value int

EXEC@return_value = [dbo].[AddToProject]
@DeptCode = N'BAT',
@ProjectTitle = N'Some Title',
@ProjectDetails = N'Some Details',
@ProjectManagerID = 3,
@RequestedBy = N'Me',
@DateRequested = N'04/27/2007',
@DueDate = N'05/04/2007',
@ProjectStatusID = 4

SELECT'Return Value' = @return_value

GO

  
I get the following errors:
 Msg 128, Level 15, State 1, Line 1
The name "BAT" is not permitted in this context. Valid expressions are constants, constant expressions, and (in some contexts) variables. Column names are not permitted.
Msg 137, Level 15, State 1, Line 1
Must declare the scalar variable "@ProjID".
Msg 515, Level 16, State 2, Procedure AddToProject, Line 17
Cannot insert the value NULL into column 'ProjID', table 'NYCEDC.dbo.tbl_Project'; column does not allow nulls. INSERT fails.
 
If I run just the GetProjID sp, I get the following error:
 Must declare the scalar variable "@ProjID".
 -------------------------------------
What I'm trying to do is, get a bunch of values from the aspx page, insert the DeptCode into the field DeptCode of the table 'tbl_ProjectNumber'+DeptCode so that the IDENTITY value field 'ProjectNumber'+DeptCode can increment by 1. After 'ProjectNumber'+DeptCode has incremented, I want to run the GetProjID sp so that I can insert ProjID into the 'tbl_Project' table along with the other values taken from the aspx page. ProjID is the primary key for the 'tbl_Project' table so it needs to be added along with the other values (other they obviously can't be added). I'm running the AddToProject as a Transaction to make sure that if more than 1 person is adding a project at the same time, the project numbers and other information don't get messed up.
 
Any help would be appreciated.
Thanks.