I'm having a similar problem. Here's the code:
 Declare @sql_stmt nvarchar(250)
 Declare @template_name varchar (30)
 Declare @table_name varchar (31)
 Declare @field_name varchar (30)
 set @template_name = 'hpi_oncprostate'
 set @field_name = 't_dec'
 set @table_name = @template_name + '_'
 delete from  fields_master Where field_name=...