'Declaration
    Dim Txtdynamic As TextBox
    Dim intcount As Integer
    Dim inttxtcnt As Integer

Add the below 

 Try

        'to check the textbox for empty
            If Not TextBox1.Text Is String.Empty Then
                inttxtcnt = TextBox1.Text
            Else
                Exit Sub
            End If

            'To create the dynamic text box and add the controls to Flowlayout panel
            For intcount = 0 To inttxtcnt - 1
                Txtdynamic = New TextBox
                Txtdynamic.AutoSize = True

                'set the font size
                Txtdynamic.Font = New System.Drawing.Font("Verdana", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
                Txtdynamic.Name = "txtdynamic_" & intcount & "_mycntrl"
                FlowLayoutPanel1.Controls.Add(Txtdynamic)
            Next
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try


'To get the values from dynamic created values

  Dim intdyncnt As Integer
        'to check the textbox for empty
        If Not TextBox1.Text Is String.Empty Then
            inttxtcnt = TextBox1.Text
        Else
            Exit Sub
        End If

        Try

            'To get the dynamic text box values which is added in flowlayout panel
            For intcount = 0 To inttxtcnt - 1
                If Not TextBox1.Text Is String.Empty Then
                    If FlowLayoutPanel1.Controls(intcount).Name = "txtdynamic_" & intcount & "_mycntrl" Then
                        If CInt(Txtdynamic.Text) > 0 Then
                            intdyncnt += CInt(FlowLayoutPanel1.Controls(intcount).Text)
                        End If
                    End If
                End If
            Next
            MsgBox(" The sum of the values is " & intdyncnt)
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try