Trying to get total hours

See more:

VB

ASP.NET

.NET4.5

Hello all. Thanks for reading my post. I developed a "time clock" to keep track of hours worked. I have the hours worked for the day. I need to get the total hours for each employee. I am hitting a wall. I have two calendar controls to select a date range. I am able to display the info. from the database into a gridview which includes daily hours and the employee's name. How can I get the total hours for each employee for the selected date range? They don't have to go into the gridview. I could display names and total hours using labels placed below the gridview. Here is the code I am using to get the data into the gridview.

Protected Sub Calendar332_SelectionChanged(sender As Object, e As EventArgs)
        'declare SQL statement that will query the database
        Dim sqlstring As String = SELECT firstname, lastname, startdate, starttime, endtime, hours FROM hoursworked WHERE startdate =  Calendar332.SelectedDate  AND startdate = Calendar333.SelectedDate   ORDER By startdate

        Dim strSQLconnection As String =  Source=SQL Server;SERVER=123abc; Initial Catalog=abc; UID=xxxxxxx;PWD=xxxxxxx;

        Dim sqlConnection As New Data.SqlClient.SqlConnection(strSQLconnection)
        Dim sqlCommand As New Data.SqlClient.SqlCommand(sqlstring, sqlConnection)
        sqlConnection.Open()

        Dim reader As Data.SqlClient.SqlDataReader = sqlCommand.ExecuteReader()

        

        GridView7.Visible = True
        GridView7.DataSource = reader
        GridView7.DataBind()
        reader.Close()
    End Sub

Thank you for any input you might be able to provide.

D-Bar


Table structure:
id - auto increment
first name
last name
startdate
starttime
endtime
hours

Data is test data like:
John Doe 2013-11-15 2013-11-15 8:00:00 AM 2013-11-15 5:00:00 PM 9:00