Quite obviously, one can't do that (just tried it).
If you need this to be more flexible, you will have to do the whole process in SAS code (the file import task in EG works in two stages: EG converts the file to a special text format and uploads it, then a data step reads theat file into a SAS dataset). For this you will have to set up a way that allows you to dynamically make the source file accessible on the SAS server. Shared network location, use of a FTP/SFTP server, ...)