Ok so this is going to be a long post (I will need to check the blog options and shrink the post sizes). This is a solution to task 1 in 6.5.3 it is based on the design given in the answers. It is NOT the only solution and you might want to comment on ways the program could be improved (think about evaluation). I have included some screen shots.

NOTE the display of the data is optional.

Option Explicit

Private Sub Command1_Click()
'This program represents a solution to 6.5.3 task 1
'The Desgin was given in the answers section
'It is not the only solution
Dim HD_up As Integer 'HD Upgrade required
Dim RAM_up As Integer 'RAM Upgrade required
Dim Mon_up As Integer 'Monitor Upgrade required
Dim Cost1 As Single 'Price
Dim Num As Integer 'Quanity
Dim Basic_Cost As Single 'Cost for Order before deliver and discounts
Dim Dis As Single ' Discount on whole order
Dim Del As Single ' delivery charge per order
Dim VAT As Single 'VAT on Order
Dim Total As Single ' Order Total
Cost1 = 499 'Set the starting cost of a machine
Del = 50 ' £50 delivery per order
Form1.Print "The basic systems costs 499" 'optional
Call Get_Comp_Spec(HD_up, RAM_up, Mon_up)
Call Calc_Cost_Of_One(Cost1, HD_up, RAM_up, Mon_up)
Call Get_Number(Num)
Call Calc_Basic_Cost(Num, Cost1, Basic_Cost)
Call Calc_discount_delivery_VAT(Num, Basic_Cost, Dis, Del, VAT)
Call Calc_total_cost(Basic_Cost, Dis, Del, VAT, Total)
Call Display_total(Total)
End Sub

Private Sub Get_Comp_Spec(ByRef HD_up As Integer, ByRef RAM_up As Integer, ByRef Mon_up As Integer)
'Check what upgrades the user wishes
HD_up = MsgBox("Do you wish to upgrade to 60GB for £30?", vbYesNo)
RAM_up = MsgBox("Do you wish to upgrade to 1GB for £50?", vbYesNo)
Mon_up = MsgBox("Do you wish to upgrade to 21 inch for £199?", vbYesNo)
End Sub

Private Sub Calc_Cost_Of_One(ByRef Cost1 As Single, ByVal HD_up, ByVal RAM_up, ByVal Mon_up)
'calculate the cost of the upgrades
If HD_up = vbYes Then
Cost1 = Cost1 + 30
Form1.Print "Hard drive upgrade £30" 'optional
End If
If RAM_up = vbYes Then
Cost1 = Cost1 + 50
Form1.Print "RAM upgrade £50" 'optional
End If
If Mon_up = vbYes Then
Cost1 = Cost1 + 199
Form1.Print "Monitor upgrade £199" 'optional
End If
End Sub

Private Sub Get_Number(ByRef Num As Integer)
'Get the number of systems ordered
'As an extension task this number could be validated
Num = InputBox("How many machines do you want?")
Form1.Print Num & " machines ordered" 'optional
End Sub

Private Sub Calc_discount_delivery_VAT(ByVal Num, ByVal Basic_Cost, ByRef Dis As Single, ByRef Del As Single, ByRef VAT As Single)
'Calculate Discount
If Num > 10 And Num <= 20 Then
Dis = Basic_Cost * 0.05 '5% Form1.Print "A discount of 5% is £" & Dis 'optional
ElseIf Num > 20 Then
Dis = Basic_Cost * 0.1 '10%
Form1.Print "A discount of 10% is £" & Dis 'optional
Else
Dis = Basic_Cost * 0 '0%
Form1.Print "A discount of 0% is £" & Dis 'optional
End If
'Calculate VAT
Form1.Print "Delivery on the order is £" & Del 'optional
VAT = (Basic_Cost - Dis + Del) * 0.175
Form1.Print "The VAT on the order is £" & VAT 'optional
End Sub

Private Sub Calc_Basic_Cost(ByVal Num, ByVal Cost1, ByRef Basic_Cost As Single)
'Calculate the cost of the order before discount and VAT
Basic_Cost = Num * Cost1 ' Cost for whole order
Form1.Print "The cost of the order before discount,deliver & VAT is £" & Basic_Cost 'optional
End Sub

Private Sub Calc_total_cost(ByVal Basic_Cost, ByVal Dis, ByVal Del, ByVal VAT, ByRef Total As Single)
'Calculate the Total cost of the whole order
Total = Basic_Cost + Del + VAT - Dis
End Sub

Private Sub Display_total(ByVal Total)
'Display the cost for the whole order
Form1.Print "The total for the order was £" & Format(Total, "0.00")
End Sub