ASP.NET add controls at runtime

Attached you will find a sample webform. (one .aspx and ono .vb files) We are working with Visual Studio 2008 and VB.NET, we use AJAX and Master Pages. We need to implement the functionality described below, and have preference for a solution using asp controls added dynamically and validations done in code-behind. Please, download the sample webform to understand the explanation. In the example we have 2 groups. The user can select any checkbox in any group. Then the user clicks one button. And we validate if the checkboxes selected in the button's group match the target. e.g.: checked on the second group, first and third checkboxes... and the user clicks the second group button... is OK, because 20+50 = 70 (the target for this group) e.g.: checked on the first group, second, third, fourth and fifth checkboxes, then click this group button... is NOT OK, because 2+3+4+5=14 (the target is 10) if NOT OK, we want to show a warning message, could be a label near the button. And the user can continue to select/deselect checkboxes, is the page is not reloaded, better. if OK, we will continue to other page and we need to know which group button was selected (e.g. 1 or 2) and which checkboxes were selected. Important: We could have any number of groups and every group could have any number of items.