Inserting State Names Based On Telephone Numbers

I have a large data set (excel file), of "Names", "Phone Numbers", and i need to sort this based on the States that correspond with the Phone numbers. The states currently do not exist in the spreadsheet, so my current problem is trying to insert those states into the spreadsheet.

There are over 100 area codes in the data set, so i'll likely have to write a large "If" statement in VB to run through them all, but that shouldnt be a problem.

NAME, PHONE, STATE
Bleh, 555-555-5555, =ChkState(B2)

I've been playing around with the VB Stuff in Excel and this is what i've come up with for trying to insert the State field

Function ChkState(pVal As String) As Long

Dim AreaCode As String
Dim StateAbrv As String

AreaCode = Left(pVal, 3)

If AreaCode = "201" Then
StateAbrv = "Test201"
ElseIf AreaCode = "203" Then
StateAbrv = "Test203"
ElseIf AreaCode = "555" Then
StateAbrv = "Test555"
Else
StateAbrv = "0"
End If
MsgBox StateAbrv
End Function

I'm fairly new to this VB stuff, my main problem stems from trying to insert the "StateAbrv" back into the Cell for the spreadsheet.