Hi Louis,
As long as you have the row already created you can definitely use a button to populate but it will require setting a value with an index and that isn't supported in the browser. So, we created a command in our qRules library of common commands called SetValue which lets you do this and even has cool filtering capabilities. qRules is a common library of functions, so it is code, but it can easily be deployed to a SharePoint 2010 browser form if the site is configured to allow sandbox. If not, you can still do it as an admin deployed form.
Best of luck!