Thanks eladsal, Now, I am using VBA codes, and call epanet2.dll codes in the tookit package. I have used the following code to retrieve link IDs and it works.
"Public Function getLinkId(ByVal Index As Long) As String
Dim s As String
s = String$(255, vbNullChar)
error = ENgetlinkid(Index, s)
getLinkId = Left(s, InStr(1, s, vbNullChar) - 1)
End Function "
But what Public Function can be used to set new link and node IDs?.