'Dependencies: none

'Note that all parameters are passed by reference. They _will be changed_.
Sub Interchanger(RT1 As Double, RT2 As Double, RP1 As Double, RP2 As Double, _
    RG1 As Double, RG2 As Double, RG3 As Double, RG4 As Double, RE2 As Double, _
    RT5 As Double, RT6 As Double, RT8 As Double, RT9 As Double, RTE As Double, _
    hasError As Boolean)
'Transfer interchanger. This is going to be kind of messy.
    Dim T1, T2, P1, P2, G1, G2, G3, G4, E2, T5, T6, T8, T9, TE As Double
    Dim del, delta, T9C As Double
    Dim iDelp5 As Integer 'Fix(del + 0.5) is this now
    Dim iter As Integer

    Dim skipToggle As Boolean
    skipToggle = False

    T1 = RT1
    T2 = RT2
    P1 = RP1
    P2 = RP2
    G1 = RG1
    G2 = RG2
    G3 = RG3
    G4 = RG4
    E2 = RE2
    T5 = RT5
    T6 = RT6
    T8 = RT8
    'T9 = RT9 In original code, but does nothing. Left for ~posterity~
    TE = RTE
    T9 = T2
    iter = 0

    Do
        iter = iter + 1
        T5 = (T9 * (P2 + G4) - T2 * T2) / G3
        T6 = (T1 * E2 * G1 + T9 * (P1 + G3) * (1# - E2)) / (P1 + G3 - G4 * E2)
        T8 = (T1 * G1 + T6 * G4) / (P1 + G3)
        'Escape the loop and skip the piece right afterwards (goto 3)
        If (T8 < T1) Then
            skipToggle = True
            Exit Do
        End If

        T9C = (T5 * G3 + T6 * G4 - T8 * G3) / G4
        delta = Abs(T9 - T9C)
        del = 10000# * delta
        iDelp5 = del + 0.5

        'Maybe escape the loop and goto 2
        If (iDelp5 <= 1) Then Exit Do

        If (iDelp5 > 100) Then
            T9 = T9 + 0.05 * (T9 - T9C)
        ElseIf (iDelp5 > 10) Then
            T9 = T9 + 0.03 * (T9 - T9C)
        ElseIf (iDelp5 > 5) Then
            T9 = T9 + 0.01 * (T9 - T9C)
        ElseIf (iDelp5 > 2) Then
            T9 = T9 + 0.005 * (T9 - T9C)
        Else 'If (iDelp5 > 1)
            T9 = T9 + 0.002 * (T9 - T9C)
        End If
    Loop

    'The first segment after the loop, i.e., 2. Skip this if it was the first
    'exit option from the loop.
    If (skipToggle = False) Then
        TE = (T9 - T6) / (T9 - T8)
        hasError = False
    'The second segment after the loop, i.e., 3. This is the bad outcome.
    Else
        hasError = True
    End If

    'This gets executed in both outcomes before the return.
    RT1 = T1
    RT2 = T2
    RP1 = P1
    RP2 = P2
    RG1 = G1
    RG2 = G2
    RG3 = G3
    RG4 = G4
    RE2 = E2
    RT5 = T5
    RT6 = T6
    RT8 = T8
    RT9 = T9
    RTE = TE
End Sub