Function getGCD(a As Integer, b As Integer) As Integer

    Dim c As Integer ' Used to store value of b during while loop

    ' Check for error condition before starting while loop
    If a = 0 And b = 0 Then
        ' Store error in return var
        getGCD = CVErr(xlErrValue)
    Else
        ' Simplifies until answer is found
        Do While b <> 0
            c = b        ' holds original value of b so we can put it in a after changing b
            b = a Mod b  ' changes b
            a = c        ' store original value of b in a
        Loop
        ' Store result into return var
        getGCD = a
    End If


End Function