I'm sorry about the issue. Do you mean Excel program?
What are the full names of these XL files?
What's the full error or message when trashing them? Do you have Windows xp, vista, or 7, or 8, 10, or Mac os x 10.6, 10.7, 10.8, 10.9, 10.10, etc.?
Please reply at the box below. Thank you