How do you do multiple regresson in Excel (to show Mediation)?

How do you do multiple regresson in Excel (to show Mediation)?

Does anyone know how to use Excel to do multiple regession to show full and partial mediation using Baron and Kenny's method and alternatively Preacher and Hayes. I've been looking around for algorithms in R or even Statistica but most of these are blackboxes. If there are any datasets (that can be transferred or are in an .xls file) then it would be better.