Here's a start. Not sure if you also need to know the code for the importing. If so, I can provide that as well. Sorry to do this in pieces. It's been a crazy day.
Sub findfiles(dStartDate As Date, dEndDate As Date, strFolder As String)
Dim strHours As String, dDate As Date
strHours = ".09.00"
dDate = dStartDate
Do While dDate < dEndDate
If Dir(strFolder & "revp_daily_extract.txt" & Format(dDate, "mmddyy") & strHours & ".arc") > "" Then
'import data
End If
strHours = IIf(strHours = ".09.00", ".21.00", ".09.00")
dDate = dDate + 1
Loop
End Sub
Let me know if you need more.
E