Refine your complex spreadsheet model to improve efficiency.

a) The user needs to enter at least one of the following contact details: Home Phone, Mobile or E-mail address. If all of these have been left blank, then the user needs to receive feedback to ensure that they enter one value.

The maximum garden length, width and radius, Gareth can cater for are:

Length 1000m

Width 750m

Radius 200m

Implement validation to ensure that user entry does not exceed these values.

b) Implement password protection into you workbook to ensure that no unauthorised persons can access the data.
P5

c) Add two additional sheets to your workbook - one named Invoice and the other named Menu.

d) Add macro buttons to each of the four worksheets to enable the user to fully navigate around the workbook. Include a Quit button on the menu.