As someone who takes on the occasional work experience student...
It can be daunting to a pharmacist to try and think of activities that can be included in a work experience programme. We're also a little bit stuck with needing to get any staff we employ on an approved course within 3 months unless they are an undergraduate so your pharmacist may be thinking about this too. I've had work exp students tell me that they want to be a doctor/nurse/drug rep and I start with the basis that their half day with me will be tailored to that. If someone tells me that they want to be a pharmacist I try and slot in 4 full days and ensure that they see as much as possible. It's a lot easier if they have some ideas though and to avoid falling foul of the NVQ2 rule I never extend the experience programme beyond 3 months.
The first thing to do is to be honest. Why are you asking for work experience? If it is to look good on the application form then he can't really help you. If it is because you want to see the range of services provided by a pharmacy, to learn more about the communication and team working skills required to be successful in pharmacy, to learn how to use the BNF, to understand the basics of assessing whether a prescription should be dispensed or not then that gives him a guide on which to base the experience. It will also mean that you can explain the benefits of your work experience more fluently in any applications or interviews.
Think of it in terms of finishing the sentence "By the end of this experience I want to be able" and start 5 sentence endings with the word "to...". 5 sentences will then equal objectives and you should never have more objectives than you can count on the digits of one hand!
If I was selecting between 2 students wanting experience I would always go for the one who had some clear objectives for wanting to work with me and learn from my team rather than one who told me that they were committed to being a pharmacist - I'd suspect the latter was just trying to gain a point for the UCAS application.
For those reading the thread who haven't managed to get work experience in a pharmacy - take heart! The best undergraduate students I took on for vacation programmes had worked as a bus driver, in Woolworths, as a betting assistant and in Dixons. None of them were recruited on their pharmacy experience but because they were able to demonstrate good communication skills, effective team working and had held positions of trust.