declare @dbname varchar(128) = 'TestDB',
        @filedate varchar(64) = '20121214210000',
        @sqlcmd varchar(max);

SET @sqlcmd = 'BACKUP DATABASE ' + @dbname + ' TO DISK = ''H:\Preupgrade\ Backups\' +
              @dbname + '_' + @filedate + '''' + ' WITH NOFORMAT, NOINIT, ' +
              'NAME = ' + '''' + @dbname + @filedate + '''' + ', SKIP, REWIND, NOUNLOAD, STATS = 10';

print @sqlcmd;

declare @dbname varchar(128) = 'TestDB',
        @filedate varchar(64) = '20121214210000',
        @sqlcmd varchar(max);

SET @sqlcmd = 'BACKUP DATABASE ' + @dbname + ' TO DISK = ' + CHAR(39) + 'H:\Preupgrade\ 
              Backups\' + @dbname + '_' + @filedate + CHAR(39) + ' WITH NOFORMAT, NOINIT, ' + 
              'NAME = ' + CHAR(39) + @dbname + @filedate + CHAR(39) + ', SKIP, REWIND, NOUNLOAD,  
              STATS = 10';

print @sqlcmd;

declare @dbname varchar(128),
        @filedate varchar(64);
declare @diskfile varchar(256) = 'H:\Preupgrade\Backups\' + @dbname + '_' + @filedate;
declare @filename varchar(256) = @dbname + @filedate;

declare @SQLCmd varchar(max) =
'BACKUP DATABASE @dbname
TO DISK = @diskfile
WITH NOFORMAT,
     NAME = @filename,
     SKIP,
     REWIND,
     NOUNLOAD,
     STATS = 10;';
declare @Params @varchar(max) = '@dbname varchar(128), @diskfile varchar(64), @filename varchar(256)';

exec sp_executesql
    @SQLCmd,
    @Params,
    @dbname = @dbname,
    @diskfile = @diskfile,
    @filename = @filename;