Can This Be Done Just In Database (I Have Given Codes)

Hi , I have a database that records the users entrance to a building.The dates are recorded also .I have written some codes that to detect the period of dates that the person has entered.Lets say that a person named as jhon has entered the building on the days 02/08/2006 and 05/08/2006 and 11/08/2006 .Those dates are formated as dd/mm/yyyy . So that john has entered building for 3 times and the periods for the dates are one after another entrance is 3 days + 6 days =9 days .If you divide 9 by 3 we get the arithmetic average number 3 .So that we can say as john visits this building every 3 days and we can guess the next day that he may come.
I have coded this and works great .I will paste the codes to the end of my message.But a master programmer friend of mine has said that I should have get this result by without writing code , by just using sql database .But some kind of stored procedure I mustn't use.So that I thought it can be done by views in sqldb .By using sql server enterprise manager I tried to use views but I could not succees.
Can anyone guess this ?
Here are my vb codes ...
database data types :
entry_id : int , identity
user_id : int
movie : nvarchar (50)
dateenter : datetime
stored procedure that selects the data from db:
CREATE PROCEDURE veri_al
    (
        @user_id int
    )
AS
SELECT entry_id ,user_id, movie, dateenter from uye_aktiviteleri
where (user_id=@user_id) ORDER BY entry_id ASC
GO
 

Code:
Dim conn As New SqlClient.SqlConnection
        conn.ConnectionString = "data source=localhost;initial catalog=AFM;uid=nusret;pwd=araz"
        Dim command As New SqlClient.SqlCommand
        command.CommandText = "[veri_al]"
        command.CommandType = CommandType.StoredProcedure
        command.Connection = conn
        command.Parameters.Add("@user_id", SqlDbType.Int, 4).Value = Val(TextBox1.Text)
        If Not IsNumeric(TextBox1.Text) Then
            Exit Sub
        End If
        Try
            Dim adapter As New SqlClient.SqlDataAdapter
            adapter.SelectCommand = command
            Dim ds As New DataSet
            adapter.Fill(ds, "uyeler")
            DataGrid1.DataSource = ds.Tables("uyeler")
            Dim recordcount As Integer 'Found the recordcount
            recordcount = ds.Tables("uyeler").Rows.Count

            Dim mydatarow_ilk As DataRow
            Dim mydatarow_son As DataRow
            'in stored procedure I used ORDER BY entry_id ASC so that first datarow
            'will always be the first visit date and the last record of the
            'datarow will be the last visit date
            mydatarow_first= ds.Tables("uyeler").Rows(0)
            mydatarow_last = ds.Tables("uyeler").Rows(recordcount - 1)
            Dim first_date As String
            Dim last_date As String
            first_date = mydatarow_first("dateenter")
             last_date =mydatarow_last("dateenter")
            Dim average_ As Integer
            'What is the aveare of the visits
            ortalama = DateDiff("d", first_date , last_date ) / recordcount
            Label2.Text = "Member had visited for " & recordcount & "times"
            Label3.Text = "by average he/she comes here " & ortalama & " day to another."
            Dim last_time_visit As Integer
           last_time_visit = DateDiff("d", last-date , DateTime.Today())
            Label4.Text = "Until the last visit it had been" & last_time_visit & " days"
            Label5.Text = "Guess for the next visit is" & DateAdd("d", average_ , last_date)
            ' MsgBox("average visits" & ortalama & " days" )
        Catch z As Exception
            MsgBox("error : " & z.Message())
        Finally
            MsgBox("Successfully calculated")
        End Try
    End Sub