The Show for mesagge box is never executed because it's after the return statement. Try changing the order of the lines
if (totalMinutes <= 60)
{
MessageBoxResult result = MessageBox.Show("Need Attention", "Confirmation");
return true;
}
Also note that if this code is from inside a property, it's probably a good idea to rethink the design so that you won't show message box inside a property getter.