I need to create a database in which:

When selling a book, its price will be fetched from the table using the DLookup command and the stock will be reduced by the number of books sold.
Selling of books will be through the use of forms and subforms.
Create an invoice report to bill the customer after the selling took place. This can be done by using a button on the Invoice form.
Create a report that will calculate all tax due. That is the totals of the 5% collected and to be paid to the government. After printing the report, an indication of all amounts cleared with tax is needed in order not to include the amount again in the next period.

i'd be grateful if any1 could help me create this.
Thank You Very much