T-SQL (SS2K8) :: Check Variable Values Dynamically

I have created dynamic sql to declare variables based on columns from the table and i set values to those variable now here is the issue . i want to check the variable values how do i do that dynamically

drop table test
create table test
(
id varchar(10) not null,
col1 varchar(10) ,
col2 varchar(10)

[Code] .....

Now my next step is verify if the variable is blank or not how do i do that ?

How do i verify all of the columns one after the other .

I am after the statement like this dynamically

-- IF NOT (@col1 = '') THEN set @SQL = @SQL + '[col1] = ' + @col1 + ' '
--IF NOT (@col2 = '') THEN set @SQL = @SQL + '[col2] = ' + @col2 + ' '

I need to check if the columns are blank or not dynamically as i do not want to hard code the column names there.