I ended up solving this by using the below code instead of xlswrite().
writecell(c,outFile,'UseExcel',true,'WriteMode','overwritesheet','Sheet','Data');
My ML code to create the formula for Excel did not need to change, nor did I need to use "CalculateFull()" as Sreeram recommended.
Also note that I needed to have this writecell after I had already created the sheets that I needed to reference in the Excel formulas (i.e. I needed to create the "CRETAinfo" sheet before I used writecell() for the sheet with the Excel formulas.