Another approach
Say you create a class clsBitcoinPublicKey
In the class module create an ADDITIONAL subroutine, that acts as you would want the real constructor to behave. Below I have named it ConstructorAdjunct.
Public Sub ConstructorAdjunct(ByVal ...)
...
End Sub
From the calling module, you use an additional statement
Dim loPublicKey AS clsBitcoinPublicKey
Set loPublicKey = New clsBitcoinPublicKey
Call loPublicKey.ConstructorAdjunct(...)
The only penalty is the extra call, but the advantage is that you can keep everything in the class module, and debugging becomes easier.