Problem in DataGrid

Question

hi,
I am using .net 1.1 version.
The problem is i have used one datagrid which contains some data columns and one checkbox column.
Datagrid contains nearly 50 records and 50 checkboxes.(i.e) each record contains checkbox.
below  the datagrid an image button is placed.if i didn't select any checkboxes and click on the image button it should tell please select any two checkboxes for compare.
how to do this if i used .net 2.0 then the OnClientClick event can be used but i am using .net 1.1 so please any one help me....
Regards,
Prakash