Input validation etc

Hi People,

I was wondering if anybody could help me with the following VB problem?

1st) I have a calculator process and I need to validate the input. Know I have done a catch and try for checking if the input is numeric or not. But is there a simple way to check if the input in the calculator is plus or minus numbers.

I want to prevent minus numbers form being inputed.

2nd) I am trying to access two different tables with in one database. I have set up a form where that table can be displayed, but it is trying to look up the wrong table and I dont know how to get it too look up the other table.

The following is the code that I have to acess the database and bring the information from the tables into memory:-

Code:

Dim dt As New DataTable
    ' create and object called dt of the class datatable
    Dim rowindex As Integer     ' create an integer to hold which row of the table we are at
    ' Create a string with the appropriate connection details ie data provider and data source
    Dim connStr As String = "Provider = Microsoft.Jet.OLEDB.4.0;" & "Data Source = EngineerJobs.mdb"
    ' create a string containing a valide SQL statement that will return data
    Dim sqlStr As String = "SELECT * FROM Engineers_Allocated, Engineers"

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        '
        
        'Opens a connection to a database and extracts data from it
        '
        'empty datatable for refilling
        
        dt.Clear()

        'Create a link to the database via a datatadapter
        Dim DataAdapter As New OleDb.OleDbDataAdapter(sqlstr, connStr)
        'fill the datatable created with the contents of the dataAdaptor
        DataAdapter.Fill(dt)
        'Destroy the dataAdaptor - saves memory etc
        DataAdapter.Dispose()
        'move one records details to the textboxes - as rowindex is initially zero this is the first record

Is there a different way to get information from the database and put it into the form?

For the form I have the next record and previous record buttons which relate to the following code:-

Code:

Sub UpdateTextboxes2()
        '
        
        'Updates the textboxes on the form with data held in the row indicated by the rowindex variable

        
        Dim Fieldno As Integer = 0


        'Move the contents of record into the fields 
        TxtJobID.Text = CStr(dt.Rows(rowindex)(0))  'by position
        txtengineer.Text = CStr(dt.Rows(rowindex)("EngineerNO")) 'by name
        txtjob.Text = CStr(dt.Rows(rowindex)(2))

If anybody can help me with this I would be very thankfull as this is all to do with an Assignment for Uni that needs to be in, in the new year.

Cheers in advance peop's!