Excel is infuriating!

Excel is Microsoft's spreadsheet program. Of course, being Microsoft, they just love to make their software frustrating to use. Why on earth does the "replace" function refuse to work sometimes? I'm trying to replace every instance of an "x" with "*A1^", but because doing so results in what they label as a "broken formula", it refuses to replace any of these x's! I am, of course, aware that it results in a "broken formula", but at least it gets me half way to the correct formula and would save me a great deal of work if the damn software would just obey my instructions. Why the heck won't it allow me to change it then simply give me the message that it's a broken formula?