VS 2010 Checkbox to Textbox value (total)

Hi all,

I have 13 check boxes named cb1-13 they are on in tabpage1 in groupbox1.

And i have a "Total" box in groupbox1

Then I have 13 textboxes named dtb1 - 13 they are on tabpage2 in groupbox3 (these have values in that change weekly)

I need the "Total" box to total based on the checkboxes selected.

cb1 needs to look at the value in dtb1
cb2 @ dtb2
cb3 @ dtb3
and so on.......

Any help or guidance is appreciated.

Thanks in advance.
Chris