Private Sub Command1_Click()
Dim a As String, b As String, c As String, d As String
a = "Janet "
b = "Erin "
c = "Carolyn "
d = "Kate "
cmdDo "test^test", a, b, c, d

'после выполнения, в переменные a,b,c,d должен получить 
'другие параметры (строки) из процедуры o_OnDataArrival
End Sub

Private Sub o_OnDataArrival(ByVal bytesTotal As Long)
On Error GoTo Error_Handler
Dim strChunk As String
On Error GoTo Error_Handler
o.GetData strChunk
rtb.Text = ""
    'if header hasn't arrived
    strHeader = strHeader & strChunk
    If InStr(strHeader, Chr( 0 ) & Chr( 0 ) & Chr( 0 ) & Chr( 0 ) & Chr( 0 )) Then
     rtb = strHeader
     strHeader = ""
     strChunk = ""
    End If

    ' Как переменным  v1 ,v2 ... v10 из функции
    ' присвоить то что получим здесь ?

Exit Sub
Error_Handler:
    strHeader = ""
    MsgBox ("Error: " & Err.Number & Err.Description)
End Sub


 Function cmdDo(Routine As String, Optional v1, Optional v2, Optional v3, _
                                   Optional v4, Optional v5, Optional v6, _
                                   Optional v7, Optional v8, Optional v9, Optional v10)
Dim par As Integer
Dim strLen1 As Long, strLen2 As Long, strLen3 As Long, strLen4 As Long, strLen5 As Long
Dim strLen6 As Long, strLen7 As Long, strLen8 As Long, strLen9 As Long, strLen10 As Long
Dim Str As Variant
Dim LenStr As Variant
Dim strSend As Variant
Dim strLenAll As Long
Dim strRes As Variant
    
par =  0 
strLenAll =  0 

If IsMissing(v1) = False Then
par = par +  1                            'Parameter
Str = Str & v1 & Chr( 13 ) & Chr( 10 )      'String
strLen1 = Len(v1)                       'Len string
strLenAll = strLenAll + Len(v1)         'All Len
Else
par = par
strLen1 =  0 
strLenAll = strLenAll
End If

If IsMissing(v2) = False Then
par = par +  1 
Str = Str & v2 & Chr( 13 ) & Chr( 10 )
strLen2 = Len(v2)
strLenAll = strLenAll + Len(v2)
Else
par = par
strLen2 =  0 
strLenAll = strLenAll
End If

If IsMissing(v3) = False Then
par = par +  1 
Str = Str & v3 & Chr( 13 ) & Chr( 10 )
strLen3 = Len(v3)
strLenAll = strLenAll + Len(v3)
Else
par = par
'Str = ""
strLen3 =  0 
strLenAll = strLenAll
End If

If IsMissing(v4) = False Then
par = par +  1 
Str = Str & v4 & Chr( 13 ) & Chr( 10 )
strLen4 = Len(v4)
strLenAll = strLenAll + Len(v4)
Else
par = par
strLen4 =  0 
strLenAll = strLenAll
End If

If IsMissing(v5) = False Then
par = par +  1 
Str = Str & v5 & Chr( 13 ) & Chr( 10 )
strLen5 = Len(v5)
strLenAll = strLenAll + Len(v5)
Else
par = par
strLen5 =  0 
strLenAll = strLenAll
End If

If IsMissing(v6) = False Then
par = par +  1 
Str = Str & v6 & Chr( 13 ) & Chr( 10 )
strLen6 = Len(v6)
strLenAll = strLenAll + Len(v6)
Else
par = par
strLen6 =  0 
strLenAll = strLenAll
End If

If IsMissing(v7) = False Then
par = par +  1 
Str = Str & v7 & Chr( 13 ) & Chr( 10 )
strLen7 = Len(v7)
strLenAll = strLenAll + Len(v7)
Else
par = par
strLen7 =  0 
strLenAll = strLenAll
End If

If IsMissing(v8) = False Then
par = par +  1 
Str = Str & v8 & Chr( 13 ) & Chr( 10 )
strLen8 = Len(v8)
strLenAll = strLenAll + Len(v8)
Else
par = par
'Str = ""
strLen8 =  0 
strLenAll = strLenAll
End If

If IsMissing(v9) = False Then
par = par +  1 
Str = Str & v9 & Chr( 13 ) & Chr( 10 )
strLen9 = Len(v9)
strLenAll = strLenAll + Len(v9)
Else
par = par
strLen9 =  0 
strLenAll = strLenAll
End If

If IsMissing(v10) = False Then
par = par +  1 
Str = Str & v10 & Chr( 13 ) & Chr( 10 )
strLen10 = Len(v10)
strLenAll = strLenAll + Len(v10)
Else
par = par
strLen10 =  0 
strLenAll = strLenAll
End If

strRes = "DO " & Routine & "~" & par & "~" & "Q" _
& "~" & strLenAll & "~" & strLen1 & "~" & strLen2 _
& "~" & strLen3 & "~" & strLen4 & "~" & strLen5 _
& "~" & strLen6 & "~" & strLen7 & "~" & strLen8 _
& "~" & strLen9 & "~" & strLen10 & vbCrLf & Str
o.SendData strRes

End Function

Option Explicit

Private strHeader As String
Private m_blnHeaderArrived As Boolean
Private m_var1 As String
Private m_var2 As String
Private m_var3 As String
Private m_var4 As String
Dim WithEvents o As OSWINSCK.Winsock
---------------------

Private Sub o_OnDataArrival(ByVal bytesTotal As Long)
On Error GoTo Error_Handler
Dim strChunk As String
m_blnHeaderArrived = False
o.GetData strChunk
rtb.Text = ""
    'if header hasn't arrived
    strHeader = strHeader & strChunk
    If InStr(strHeader, Chr( 0 ) & Chr( 0 ) & Chr( 0 ) & Chr( 0 ) & Chr( 0 )) Then
     rtb = strHeader
     strHeader = ""
     strChunk = ""
     m_blnHeaderArrived = True
    End If
   m_var1 = "Din o_OnDataArrival var1"
   m_var2 = "Din o_OnDataArrival var2"
   m_var3 = "Din o_OnDataArrival var3"
   m_var4 = "Din o_OnDataArrival var4"
Exit Sub
Error_Handler:
    strHeader = ""
    MsgBox ("Error: " & Err.Number & Err.Description)
End Sub


Function cmdDo(Routine As String, Optional v1, Optional v2, Optional v3, _
                                   Optional v4, Optional v5, Optional v6, _
                                   Optional v7, Optional v8, Optional v9, Optional v10)
................................

strRes = "DO " & Routine & "~" & par & "~" & "Q" _
& "~" & strLenAll & "~" & strLen1 & "~" & strLen2 _
& "~" & strLen3 & "~" & strLen4 & "~" & strLen5 _
& "~" & strLen6 & "~" & strLen7 & "~" & strLen8 _
& "~" & strLen9 & "~" & strLen10 & vbCrLf & Str
o.SendData strRes

Do Until m_blnHeaderArrived
  DoEvents
Loop
' Call and recive data on o_OnDataArrival
v1 = m_var1
v2 = m_var2
v3 = m_var3
v4 = m_var4
m_blnHeaderArrived = False
 m_var1 = ""
 m_var2 = ""
 m_var3 = ""
 m_var4 = ""

End Function