textboxes are either enabled or disabled based on previous page ListItem selection

In one page there is a CheckBoxList with ListItems. A user will select one or more list item/s. Based on their selection, when they go to the next page, textboxes will either be read only or enabled.
My CheckBoxList look like this
<asp:CheckBoxList ID="chkPlanCategoryList" runat="server" AutoPostBack="True"> <asp:ListItem>Employee Single Plan</asp:ListItem> <asp:ListItem>Employee Plus Child Plan</asp:ListItem> <asp:ListItem>Employee Plus Spouse Plan</asp:ListItem> <asp:ListItem>Employee Family Plan</asp:ListItem> </asp:CheckBoxList> <asp:CustomValidator ID="cvPlanCategoryList" runat="server" ClientValidationFunction="ValidatePlanCategoryList" ErrorMessage="Select one or more plan category" Text="*" Display=&quo ...