How to handle multiple column conversions

I have multiple columns in a table that I only want to convert if they are not null or of the proper type. I don't really want to redirect the whole row if one of the conversions fails, rather I would just not want to do the cast or set it to another value. In this scenario is it better to use a custom script or multiple tasks The multiple tasks seems like a lot of overhead for processing the same data. Just curious how others handle this scenario as it seems as though it has come up quite often on our current project Thanks for the assistance.

-Krusty

PS: Is it possible to embed evaluation statements along with conversion statements in a task expression e.g. (len(trim([Column1])) > 0) substring([Column1], 1, 4)