@Raoof, I am an experienced ECDL expert and I do agree with proposed test by @Slawomir. Since You are in Asia (IRAN) , I do recommend the similar program available there, see link! You can find the institutions, tests...,..., !
I appreciate your input. What i meant was some comprehensive questions (2-3) for evaluating the overall ability of a person in EXCEL. Thanks a lot for your recommendation.
I would stay away from locking in into brand name or specific commercial product. My suggestion is to try to assemble a set of questions that evaluate graduates student's knowledge on use of spreadsheet software in general. The knowledge should be applicable to MS Excel, but also to GoogleDocs, Open/Libre Office, etc.
I think the answer is Yes, you can examine the students by 2-3 questions to find their skills in MS-Excel, BUT... It depends on the field they are working in.
For example, If they are supposed to deal with large data amounts, so put a question about pivot tables, and another about data extraction and transformation. If they are in the financial field, examine their ability to deal with data manipulation, reporting, and linking. etc...
In summary, you have to specify the filed, and the skills, then put the comprehensive exam depending on it.
A major part of someone's skill set with Microsoft Excel in my estimation (and I teach proficiency courses in the software) is to ask them to conduct tasks that require nesting many functions in one, each function in the nest satisfying a very particular purpose. I agree with what others have said in that Excel proficiency is highly contextual based on the domain/field, but the overarching skill for proficiency is to know what functions do and how they might be related as building blocks to solve bigger problems. Exceedingly few questions or data necessities require exactly one function. I find that to be the biggest barrier that the students I have with the software itself.
When I worked with Koreans, they gave me a set of tasks with time constraint ,"if you can finish the tasks perfectly in the given time the position is yours", else they will assess applicants based on two factors "speed and tasks' (Excel needed tasks for the job) fulfilment".