[Excel] Substitute but with wildcards?

I know how to count the number of occurrences of particular text in a cell with the "Substitute(Cell,"old text","")" type function, but... I have multiple dates in a cell, all in the format "dd/mm/yy". Is there any way to count ALL of them, regardless of the values of dd, mm and yy? I've tried "**/**/**" but it doesn't work. Thanks!