When typing in a calculation function, show a dropdown box that provides possible matches
Example 1: In the formula box when you type "Da" a tooltip suggests "DATE, DAY, DAYS, DAYSINMONTH, DAYSINYEAR.." etc
Example 2 (List/Module specific): When typing "Employees. " a tooltip suggests your available Properties or Line Items that match "Employees.Start Date,Employees.End Date, Employees.Salary..." etc