It looks like your rule is that your value is above n50, round up to the nearest 100, else round down to the nearest 100. For example, 140 rounds down to 100, 160 rounds up to 200. 240 rounds down to 200, 260 rounds up to 300. If that's true, you can do this:
Code:
Function RoundBill(billAmount)
billHundreds=fix(billAmount/100)
billRemaining=billAmount-(billHundreds*100)
if billRemaining < 50 then
RoundBill=(billHundreds)*100
else
RoundBill=(billHundreds+1)*100
end if
End Function
billAmount=RoundBill(140)
billAmount=RoundBill(160)
billAmount=RoundBill(123)
billAmount=RoundBill(1780)