How to change databases within a stored procedure or function

This one was a royal pain in the ASS!!!! Not fully correct info on the web or people saying it CAN'T be done. NEVER NEVER NEVER tell me it CAN'T be done!!!!

here is the revelant code from an SP for truncing logs. rest your weary head!!!

USE [RIXTOOLBOX]
ALTER PROCEDURE [dbo].[spTruncateLogs]

@DBName SYSNAME

AS

BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

DECLARE @command varchar(500), @LogFile VARCHAR(500), @LOGSTR VARCHAR(10);
SET @LOGSTR = '%LOG%'
SET @command = 'DECLARE c CURSOR FOR
SELECT
NAME
FROM
[' + @DBName + '].SYS.SYSFILES
WHERE
name LIKE ''' + @LOGSTR + ''';'

EXEC (@COMMAND)
OPEN c;
FETCH NEXT FROM c INTO @LogFile;

SET @COMMAND =
'ALTER DATABASE "' + @DBName + '" SET RECOVERY SIMPLE';
EXEC (@COMMAND);
CHECKPOINT

BACKUP LOG @DBName WITH NO_LOG

SET @command =
'
USE ' + @DBName + ';
DBCC SHRINKFILE (' + @LogFile + ', 1);
';

EXEC (@COMMAND);
CLOSE c
DEALLOCATE c

SET @COMMAND =
'ALTER DATABASE "' + @DBName + '" SET RECOVERY FULL';
EXEC (@COMMAND);

SET @command =
'SELECT
*
FROM
[' + @DBName + '].SYS.SYSFILES
WHERE
name LIKE ''' + @LOGSTR + ''';'

EXEC (@COMMAND);

END