Dynamically Change SSIS For Each Loop container

Hello,
I would like to modify "Files" attribute of the Foreach Loop of type File 
Enumerator. This attribute is used to set the mask (for example *.txt) to 
specify which files to include in the selection. I need to be able to change 
this mask dynamically depending on package global variable. Is this possible?
Thank you!
Michael

Use the Expressions property, and create an expression for FileSpec property that references the global variable.|||

More details on How To get to the Extressions Property -

Open the ForEach Loop Editor by double clicking ForEach Loop Container.
Select Collection on left.
Click on the + sign on Expressions
Select FileSpec for Property and On Expression select the Global Variable Name. (which holds the file property such as *.txt)

Thanks,
Loonysan