You will need to use dynamic sql statements to do this.

something like

DECLARE @sql varchar(500)

SET @sql = 'SELECT * FROM ' + @tablename + ' WHERE ID...

I found myself in the same boat.

I used a command like this:

SET @CALL = 'osql -S DATABASE -U USERNAME -P PASSWORD -Q "USE MyDataBase; ALTER TABLE My_Table ADD FLAG CHAR(1) NULL;"'

  EXEC('master.dbo.xp_cmdshell '''...