In the spreadsheet on the Sick Leave (All) tab, if cell E matches the value in Column B on the Payroll Column B then look at the date in Column F (Form approval date). If it's <= Column E on the Payroll Calendar tab, return the date in Column E from the Payroll Calendar tab FMLA_Paid-Leave-Act--EE-.xlsx
I am thinking the lookup needs to be on the "pay period" number or something that finds one match on Payroll Calendar tab. Matching on UB will only bring back the first match on the Payroll Calendar Tab.
Microsoft Excel topics include formulas, formatting, VBA macros and user-defined functions, and everything else related to the spreadsheet user interface, including error messages.