I want to have a string value prepended to a XL-style formating in a spreadsheet program (gnumeric). The current formatting is [$-f4f2]hh:mm which should take 1:00 PM as input and convert/display it as 13:00. Additionally I would like to have it prepend the character @, such that with input 5:55pm the cell converts it to @17:55.
I am asking on Super User since it was suggested as a good site for Excel-type questions in another user's Q/A on meta 1,2.
I've already tried stuff such as CONCATENATE("("a") ", [$-f4f2]hh:mm) and [$-f4f2]hh:mm & "@" based on this post.