Expressions Not Always Evaluated In Correct Order

Hello!

I have an SSIS package, run by the DTExec utility, each night. When I run my package, I assign a value to a variable (package scope) (/SET "Package.Variables[User:: psRunNo]";0154). (Note: all the variables here are strings).


Value for variable psRunNo = 0154

In the package, I have another package variable called S_SOURCE_FILE_NAME, which is an expression and that uses the variable psRunNo.


Expression for S_SOURCE_FILE_NAME = @[User:: psRunNo] + "_{TABLENAME}.txt"


So, at the beginning, the value of variable S_SOURCE_FILE_NAME is 0154_{TABLENAME}.txt with that example.

Then, I use the variable S_SOURCE_FILE_NAME in the expression used to assign the ConnectionString property of a Connection (a source file), like this:


REPLACE( @[User:: S_REJECTED_ROWS_FILE_NAME] ,"{TABLENAME}", "STADDRES")

So here for example, the final value for ConnectionString would be 0154_STADDRES.txt

Everything works nice, most of the time. Sometimes (intermittent problem), the value of the ConnectionString for one of the many Connections I have in the package is not assigned with the right value of psRunNo. The ConnectionString gets the value of psRunNo which is saved into the package (when it was deployed) instead of the value of psRunNo passed with the DTExec.

It is like if the ConnectionString value was computed before the variable psRunNo (and S_SOURCE_FILE_NAME expression) was assigned to the new value, but only for one of the connections (all my connections use the same kind of expression for their ConnectionString property).

Does somebody had similar precedence problem? Is there some settings I could use to indicate a precedence in assignation of variables ? Where does the "natural" precedence in assignation comes from in SSIS ??

Thanks!