If you are looking to store the value within the variable to be used later, you can simply use an Execute SQL Task with a single row result set. More details in the following article:

• SSIS Basics: Using the Execute SQL Task to Generate Result Sets

If you are looking to add a computed column while importing data, you must use a Derived Column Transformation within the data flow task to add a column based on another one, you can refer to the following article for more details about this component:

• SSIS Derived Columns with Multiple Expressions vs Multiple Transformations

What are you trying to accomplish by concatenating the IDs into an "IN" statement? If the idea is to use the values of the IDs to limit the results, as a dynamic WHERE clause, you may have better luck just using a lookup against either a table you maintain with the desired IDs or even a static list generated in the package with a script task. (If you can use the lookup table method it will be much easier to maintain as you only have to update a table, not your source code.)

Alternatively, you may even be able to accomplish the goal with a join. Create a temp table from the profile IDs you want to keep and join to it, or, again, use it as a lookup component. Dynamically creating a where clause using IN will come in a lot slower and will be cumbersome to maintain.