max number checkbox columns datagridview

I am working in VB.NET and have a datagridview with multiple columns, the first being a checkboxcolumn. I want to add the functionality to restrict the amount of rows the user can select. For example, I may have 10 rows of entries in the datagridview but want to only allow for 5 checkboxes to be checked. Does anyone have any ideas on how to go about this?