在运行时期间添加列以选择ssis包的语句

I have a simple package that move data from source to destination, however I want to add new column during run time. example source table contains columns a, b and c. I have a SQL task at the beginning of the package that creates a new column like a +'_'+ b based on values from another table. My question is how to add this columns to the source of the package during run time.I have a simple package that move data from sou