Converting string to number and adding

Am collecting numerical entries from text boxes and converting to numbers using:

F1 = Round(CDbl(Request.Form("amout1")),2)
F2 = Round(CDbl(Request.Form("amount2")),2)
F3 = Round(CDbl(Request.Form("total")),2)
F4 = F1 + F2

If F4 <> F3 Then
Session("ErrorMessage") = Session("ErrorMessage") & "- Your control amounts do not tie to the Total Deposit amount.<br>"
End if

etc.

Sometimes it works, but other times, although the numbers tie out, the calculated amounts are not coming up as equal. I've written the results (F3 & F4) to the screen and they equal, although the server doesn't think so.

Is this an issue with binary number conversion or something. Should I be using something other than CRnd (Delphi has something like C$ or CCurrency)???

I've tried it (first actually) without the Round piece.

Please Help!

either try cint(Request.Form("amout1")) or ccur(Request.Form("amout1"))