Can i add a button to a data entry form and on clicking it would get the customer details from a customer table, was thinking of as they type the account number it gets the details and auto fills the customer contact, address ect
No need for a button then?
If you want a lot of data, perhaps a recordset.
Why not give them a combo, with the combo holding that data in the first place?
You don't need code or a button. When the user picks the customer from the combo, the unbound controls will be automagically be filled assuming you used the method in the "autofill" link.