API declare not allow

[Vntalk]

I have created a dll using C++, now i want to use it in VB6 However
the declaration is fine using the fullpath as follow:

Private Declare Sub Principal Lib "F:\myfunction.dll" (ByVal value As String)

However, i want to declare as:

Private Declare Sub Principal Lib app.path & "\myfunction.dll" (ByVal value As String)

VB wouln'd allow me to do that. any solution ?