Use a toolbar template to create your commands. This allows you to specify a onClick event.
.ToolBar(commands =>
commands.Template("<a class='k-button k-button-icontext' onclick='customCommand()' href='#'></span>Create</a>"))
Then you can do your checking in the js function customCommand().
More info on toolbar templates: http://docs.kendoui.com/api/web/grid#configuration-toolbar.template