While you could solve it like you suggest, a much better idea (in my opinion) would be to use uigetfile.
file = uigetfile opens a modal dialog box that lists files in the current folder. It enables a user to select or enter the name of a file. If the file exists and is valid, uigetfile returns the file name when the user clicks Open. If the user clicks Cancel or the window close button (X), uigetfile returns 0.