Sub-directories

I know how to copy files from one location to another but how would I go
about copying a file from one directory into serveral - or actually all
subdirectories in a single action? Some kind of loop

Basically I want to be able to enter a filename into a text field and click
submit which would then copy the named file (which resides in the root
directory) into every subdirectory under the root (1 level only). Would be
helpful to be able to specify mutliple files to be copied at once.