NewMarkdownFile.applescript

property targetDir : "/Users/bkelly/Dropbox/Notes/"
property editorApp : "/Applications/Byword.app"

on getNewFileName()
	set fileName to (text returned of (display dialog "Enter the filename with extension" default answer "Untitled-1.md"))
	return fileName
end getNewFileName

tell application "Byword"
	set fname to my getNewFileName()
	set fullPath to quoted form of (targetDir & fname)
	do shell script "touch " & fullPath
	do shell script "open " & editorApp & " " & fullPath
end tell