How to use SetFileAttributes on multiple files (*.txt)

I'm installing a directory of files with the below. I don't know what files will be there, but the idea is to grab whatever files are there and put them into the install directory.

  SetOutPath      "$INSTDIR\MyTextFiles"

  File            "${TEXTFILESFORINSTALLER}\*.txt"

  SetOutPath      "$INSTDIR"

I'd like to set the read-only attribute on these files. I found the SetFileAttributes command which looks like what I need. The problem is, it appears to only apply to a single file. Since I don't know what files will be there, I can't explicitly call it once for each file.

Any ideas? I need to call SetFileAttributes on all the .txt files in the directory.

Thanks, that worked! Here's what I used for reference.

  ; set my text files as readonly

  FindFirst $0 $1 "$INSTDIR\MyTextFiles\*.txt"

  txtFilesReadOnlyLoop:

    StrCmp $1 "" txtFilesReadOnlyLoopDone

    SetFileAttributes "$INSTDIR\MyTextFiles\$1" FILE_ATTRIBUTE_READONLY

    FindNext $0 $1

    Goto txtFilesReadOnlyLoop

  txtFilesReadOnlyLoopDone:

  FindClose $0