Filtered pick lists

I would like to designate certain pick lists to be automatically filtered based on a selection in a previous pick list.

For example, once I pick a specific supplier from my 'supplier' pick list, I then want the 'contacts' pick list to only show those contacts that I've already assigned to that particular supplier to be available for selection rather than all contacts for all suppliers.

Another example, once I pick a specific supplier from my 'supplier' pick list, I then want the 'product lines' pick list to only show those product lines that I've already assigned to that particular supplier to be available for selection rather than all product lines for all suppliers.

This would save me a fair amount of time filling in my forms.

Thanks.