Error while running a Dynpro Application

Hi,

I am using an RFC that use GUI_DOWNLOAD FM to push the file data to an internal table, but when it comes to Dynpro application it through an error u2018Access via Null Reference is not possible u2019 (Exception 1 of GUI_DOWNLOAD) while assigning the file name ( that is coming from Dynpro application) to GUI_DOWNLOAD.

Is there any other way to push the file data to an internal table and simultaneously can be used in DynPro application?

Thanks,

Vijay Gupta