SSIS column mappings must be done in "design time". We humans do this manually in SSIS. To do it programmatically means manipulating a template SSIS pkg and then executing that...

Here's a good URL to look at to manipulate SSIS packages in a ScriptTask (as opposed to a ScriptComponent in a DataFlow):

http://bifuture.blogspot.com/2011/01/ssis-adding-derived-column-to-ssis.html

, or use the EzAPI libraries to generate a new package object in memory, too... EzAPI doesn't work so well with manipulating existing packages as there is some kludge code you'll need to do to strip out all the "decoration" XML in the .dtsx file that BIDS puts in a package.

Hennie's got a couple of other full examples, too. To me, this was all "it just works" code, as it's just not really documented by Microsoft. I did try doing some of it on my own, especially the column mappings, but got frustrated, and Hennie's code Just Works.

The main problem I have with EzAPI is working with ADO.Net connection managers as opposed to OleDB will require you to write your own code, as that class is set up as a Virtual class... but EzAPI does work from a regular .Net C#/VB.Net app...

For doing this in a Script Task, you'll need to find and make available the appropriate versions of the Microsoft.SqlServer.DtsRuntimeWrap & Microsoft.SqlServer.DtsPipelineWrap DLLs. For BIDS 2008 using 32-bit ODBC drivers, I made copies of them into c:\Windows\Microsoft.Net\Framework\v2.0.50727, then I could make references to them... They're a bit easier to find/use in BIDS 2010... You can navigate to them in their original locations, but the UI won't let you add them from where they're initially at...

CozyRoc offers a set of ScriptComponents that they say can do dynamic column mappings at run-time as well... The DtsRuntimeWrap & DtsPipelineWrap DLLs are properly linked and usable in ScriptComponents, though...