1. use a combobox and code in combobox BeforeUpdate to search the table, VBA code using DLookup like:
If Not IsNull(DLookup("loanNum", "tablename", "LoanNum=" & Me.comboboxname)) Then
If MsgBox("Loan exists. Do you want to edit.", vbYesNo) = vbYes Then
'code to go to existing record or open another form
Cancel = True
EndIf
EndIf
This isn't working at all

Giving me an error about Loan Number (that's the name of it in the table)
2. you want latest date prior to 3pm for all records in table or just for the loan number?