String Parsing And Expression Builder....

I can't figure this one out. I don't have enough knowledge of the string functions I guess.

I need to pull a value out of a variable I setup in a for each loop. The value is the filename/path of each source file being processed. Let's say the variable that has the source file path is called VAR1.

One sort of off topic thing I've noticed is when watch the variable in bebug mode and I look at the value of VAR1 it has double back slashes. Here's an example of the value of VAR1:

"\\L3KRZR6.na.xerox.net\C$\Documents and Settings\ca051731\Desktop\Project4\DPT_20070926.ver"

How come the back slashes have been doubled? And do I need to account for that when I start parsing the string value?

Anyway, I need to grab part of the filename from VAR1 and I need the value populated at the start of the for each loop container - ideally when I capture VAR1 in the for each container. I'll be using the string in drop table, create table and create index statements before the actual Data Flow task within the overall package

In the above example I need to grab the characters before the underscore and after the last \. So I'd need the string "DPT" captured in this example.

The actual string could be 1 to 3 characters long, even though this example has it as 3 long.

Underscores could exist anywhere in the actual UNC path once this package is moved to our actual system environments so I can't key off of the underscore.

Because I can't count on the string being a fixed lenght I can't just use a positional string function and grab specific text starting/ending at specific points.

Is there a way to use the various string functions in the expression builder to grab the text between the right most underscore and the right most back slashes or something like that? Ideally I'd like to setup a new expression based packed scope variable called VAR2 and build it using string functions applied to VAR1.