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Thanks guys, that all makes good sense. However, unlike any ordinary commercial situation, the volunteers can call in at any time and say like " I will be going to mum's tomorrow" or "My car is going in for repair next Tuesday" so its not quite like a an office where time unavailable can be booked long in advance, it could be for example, he/she only works mon, wed and Friday and there can be up to a hundred volunteers, so a quick glance at an ever changing situation is required.. Good thinking though and I will explore all your good advice for the solution. Cheers folks and thanks again, all very much appreciated.