Actually, I don't want to exit the sub if they've cancelled.  I want it to
loop back and ensure that they've entered a date.  Otherwise, other parts of
subsequent code will gack.

summaryDate is declared as a variant
if cancel is pressed a zero length string is returned. by testing for
this and setting summary date to an out-of-range value the code is kept
ok.

SummaryDate = DateValue(Application.InputBox("Enter Summary Reporting
Date between " & SummaryMin & " and " & SummaryMax, "Reporting Date",
SummaryMin))

if summarydate="" then summarydate=summarymin-1

If Not Application.And(SummaryDate >= SummaryMin, SummaryDate <=
SummaryMax) Then
MsgBox "Invalid date. Please re-enter"
End If
Loop Until Application.And(SummaryDate >= SummaryMin, SummaryDate <=
SummaryMax)

Whoops - used msgbox instead of inputbox -

Dim  SummaryMin As Date
Dim  SummaryMax As Date
Dim  SummaryDate As Date
Dim  sSummaryDate as String
Dim msg1 as String

msg1 = "Enter Summary Reporting Date between " & _
  SummaryMin & " and " & SummaryMax
   Do
      sSummaryDate = InputBox(msg1, _
          "Reporting Date",SummaryMin)
   if sSummaryDate = "" then Exit sub
    SummaryDate = cDate(sSummaryDate)
      If  SummaryDate < SummaryMin or _
        SummaryDate > SummaryMax Then
           MsgBox "Invalid date. Please re-enter"
     End If
  Loop Until SummaryDate >= SummaryMin And _
     SummaryDate <= SummaryMax

If you want to validate that it is a date, then post back with how you want
to handle it.