Help with InputBox for Date Range

I have this code that I use, that works for what I need. I can go into the code and change the number of days to search, ie 30, 60, 90, 180, etc. I would like to be able to have an InputBox pop up that would allow me to enter the number of days to search before hand. Thanks for your help. This forum is invaluable!

Sub Expirations()
With Sheets("Expirations")
    .Rows(4 & ":" & .Rows.Count).Delete
End With
Set ws1 = Worksheets("Expirations")
OpenRow = 4
For Each ws In ThisWorkbook.Worksheets
    If ws.Name <> "Expirations" Then
        For Each Cell In ws.Range("AJ12:AJ" & ws.Cells(Rows.Count, "AJ").End(xlUp).Row)
            If Cell.Value > Date And Cell.Value <= DateAdd("d", 30, Date) And Cell.Value <> Empty Then
            ws1.Range("A" & OpenRow & ":AX" & OpenRow).Value = _
            ws.Range("A" & Cell.Row & ":AX" & Cell.Row).Value
            OpenRow = OpenRow + 1
            End If
        Next
    End If
Next
End Sub

-George