Issue an IP address based on condition, cell value of 1

I am trying to create an Excel Function which issues an IP address based on a flag condition. The flag is the presence or absence of a 1.

If a 1 is present then an IP address should be issued.

The function is not taking the flag condition into account and issuing an IP address regardless.

Function GetNextIP_002(text As Variant)

Dim ip As String
Dim ip_addr() As String
Dim ip_next As String
Dim cell As Range

ip = text
ip_addr = Split(ip, ".")
ip_next = Trim(Str(Val(ip_addr(3) + 1)))

If ip_next = 256 Then
    ip_next = 0
    ip_addr(2) = 1
End If

For Each cell In Range("E5:E30")
    If cell.Value = " " Then
        GetNextIP_002 = " "
    ElseIf cell.Value = "1" Then
        GetNextIP_002 = ip_addr(0) & "." & ip_addr(1) & "." & ip_addr(2) & "." & ip_next
    End If
Next cell

End Function

You wouldn't want to use a for...next loop in a function like this if you are going to use the function in all of those rows. The problem is in G5, the function will loop through all of E5:E30, and output the final result to G5. Then in G6, it will loop through all of E5:E30 again, and output the final result to G6. And so on. Since the last row in your loop E30 has a 1 flag, then anywhere you use this function will end up reading that E30 1 flag.

I've preserved your code as much as possible and moved some things around to make it a sub instead of a function. This should work as you expected:

Sub GetNextIP_002()

Dim ip As String
Dim ip_addr() As String
Dim ip_next As String
Dim cell As Range

ip = Range("G4")

For Each cell In Range("E5:E30")
    
    If cell.Value = " " Then
        cell.Offset(0, 2) = " "

    ElseIf cell.Value = "1" Then
        
        ip_addr = Split(ip, ".")
        ip_next = Trim(Str(Val(ip_addr(3) + 1)))
        
        If ip_next = 256 Then
            ip_next = 0
            ip_addr(2) = 1
        End If
        
        ip = ip_addr(0) & "." & ip_addr(1) & "." & ip_addr(2) & "." & ip_next
        cell.Offset(0, 2) = ip
        
    End If
Next cell

End Sub