' class cDrob 
Option Explicit
Public V1 As String
Public V2 As String
Private Property Get Numerator1() As String
    Numerator1 = Split(V1, "/")( 0 )
End Property
Private Property Get Numerator2() As String
    Numerator2 = Split(V2, "/")( 0 )
End Property
Private Property Get Denominator1() As String
    Denominator1 = Split(V1, "/")( 1 )
End Property

Private Property Get Denominator2() As String
Denominator2 = Split(V2, "/")( 1 )
End Property

Public Function Multi() As String
    Multi = CStr(CLng(Numerator1) * CLng(Numerator2)) & "/" & _
    CStr(CLng(Denominator1) * CLng(Denominator2))
End Function

 ' end class 
pulbic sub Test
 Dim Drob As cDrob

 Set Drob = New cDrob
 Drob.V1 = "5/9"
 Drob.V2 = "6/8"
 Debug.? Drob.Multi
End Sub