vb.net - visual basic function discounts 1 and 2 -

i'm working on code class , i'm having trouble function part.

i have this. need function accepts subtotal , calculates discount using subtotal > 200 discount of 1% subtotal > 100 discount of .5%

i struggling functions , need if point me in right direction please , thank you.

public class form1     const consthandwashprice decimal = 10d     const constinteriorshampooprice decimal = 30d     const constcarwaxprice decimal = 25d     const constengineshampooprice decimal = 15d     const constinteriorvacuumprice decimal = 16d     const constoilchangeprice decimal = 34.95d     const construstproofingprice decimal = 89.99d     const consttirerotationprice decimal = 15d     const constalignmentprice decimal = 63.88d     const constfrontbrakesprice decimal = 75.66d     const constrearbrakesprice decimal = 78.9d     dim discount decimal     dim total decimal     dim subtotal decimal     dim customername integer     dim address integer  private sub cbservices_selectedindexchanged(sender object, e eventargs) handles cbservices.selectedindexchanged     dim index integer     dim price decimal     dim msg string      index = cbservices.selectedindex      if index = 0         price = consthandwashprice         total += consthandwashprice         subtotal += consthandwashprice     end if     if index = 1         price = constinteriorshampooprice         total += constinteriorshampooprice         subtotal += constinteriorshampooprice     end if     if index = 2         price = constcarwaxprice         total += constcarwaxprice         subtotal += constcarwaxprice     end if     if index = 3         price = constengineshampooprice         total += constengineshampooprice         subtotal += constengineshampooprice     end if     if index = 4         price = constinteriorvacuumprice         total += constinteriorvacuumprice         subtotal += constinteriorvacuumprice     end if     if index = 5         price = constoilchangeprice         total += constoilchangeprice         subtotal += constoilchangeprice     end if     if index = 6         price = construstproofingprice         total += construstproofingprice         subtotal += construstproofingprice     end if     if index = 7         price = consttirerotationprice         total += consttirerotationprice         subtotal += consttirerotationprice     end if     if index = 8         price = constalignmentprice         total += constalignmentprice         subtotal += constalignmentprice     end if     if index = 9         price = constfrontbrakesprice         total += constfrontbrakesprice         subtotal += constfrontbrakesprice     end if     if index = 10         price = constrearbrakesprice         total += constrearbrakesprice         subtotal += constrearbrakesprice     end if      msg = cbservices.items.item(index) & vbtab & formatcurrency(price)      lbss.items.add(msg)        lblsubtotal.text = formatcurrency(subtotal)   end sub  private sub cleartoolstripmenuitem_click(sender object, e eventargs) handles cleartoolstripmenuitem.click     lbss.items.clear()     lbprint.items.clear()     lblsubtotal.text = ""     txtad.text = ""     txtcn.text = ""     subtotal = 0 end sub  private sub exittoolstripmenuitem_click(sender object, e eventargs) handles exittoolstripmenuitem.click     if msgbox("are sure want exit?", msgboxstyle.okcancel) = msgboxresult.ok         application.exit()      end if end sub  private sub printtoolstripmenuitem_click(sender object, e eventargs) handles printtoolstripmenuitem.click      dim index integer        lbprint.items.add("sam's customer care")     lbprint.items.add(environment.newline)     lbprint.items.add("bill to:" & txtcn.text.tostring & vbtab & txtad.text.tostring)      lbprint.items.add(environment.newline)      while index < lbss.items.count         lbprint.items.add(lbss.items(index))         index += 1     loop     lbprint.items.add("--------------------------------------------------------------------------")     lbprint.items.add("subtotal: " & formatcurrency(subtotal))     lbprint.items.add("discount: " & formatcurrency(discount))     end sub 

are looking function given total makes discount? this?

private function getdiscountedtotal(subtotal decimal) decimal    return if(subtotal > 100, if(subtotal > 200, subtotal - (subtotal * 0.1d), subtotal - (subtotal * 0.5d)), subtotal) end function 

example of usage

subtotal = getdiscountedtotal(subtotal)