Excel Graphing Calculator

I have been working for quite a while on an excel graphing calculator and am finally done. it is not nearly as powerful as desmos, or other graphing utilities. for example all equations have to be in y= format, and it cannot do anything too complex such as x factorial. (compare to desmos), but it is great for exponential equations, and includes a user-defined SIGMA function, which I designed myself with help from this forum, because i couldn't find an equivalent anywhere else. for more help, click the ? in the first userform that pops up.