erlang macro giving wrong required agents vs. calls forecasted

[tundra]

How come using the erlang method, when I have 0 (zero) calls, it is giving me a requirement of 1 agent?

here's the macro for the erlang used:
ublic Function AgentsASA(ASA As Single, CallsPerHour As Single, AHT As Integer) As Long
'Copyright © T&C Limited 1996, 1999, 2001
'Calculate the number of agents required to service a given number of calls to meet the average speed of answer
' ASA is the Average Speed of Answer in seconds
' CallsPerHour is the number of calls received in one hour period
' AHT is the call duration including after call work in seconds e.g 180
Dim BirthRate As Single, DeathRate As Single, TrafficRate As Single
Dim Erlangs As Single, Utilisation As Single, C As Single, AnswerTime As Single
Dim NoAgents As Long, MaxIterate As Long, Count As Long
Dim Server As Single
On Error GoTo AgentAError
If ASA < 0 Then ASA = 1
BirthRate = CallsPerHour
DeathRate = 1800 / AHT
'calculate the traffic intensity
TrafficRate = BirthRate / DeathRate
'calculate the number of Erlangs/hours
Erlangs = Fix((BirthRate * (AHT)) / 1800 + 0.5)
'start at number of agents for 100% utilisation
If Erlangs < 1 Then NoAgents = 1 Else NoAgents = Int(Erlangs)
Utilisation = TrafficRate / NoAgents
'now get real and get number below 100%
While Utilisation >= 1
NoAgents = NoAgents + 1
Utilisation = TrafficRate / NoAgents
Wend
MaxIterate = NoAgents * 100
'try each number of agents until the correct ASA is reached
For Count = 1 To MaxIterate
Server = NoAgents
Utilisation = TrafficRate / NoAgents
C = ErlangC(Server, TrafficRate)
AnswerTime = C / (Server * DeathRate * (1 - Utilisation))
If (AnswerTime * 1800) <= ASA Then Count = MaxIterate
If Count <> MaxIterate Then NoAgents = NoAgents + 1
Next Count

AgentAExit:
AgentsASA = NoAgents
Exit Function

AgentAError:
NoAgents = 0
Resume AgentAExit
End Function