i mean can i call this api with callapibyname function (with out declaration)?

Strptr Can Be Fully Replaced Without Any Problems
KarCrack made some error Try This

'KERNEL32
Private Declare Function VarPtr__ Lib "KERNEL32" Alias "MulDiv" (ByRef a As Any, Optional ByVal b As Long = 1, Optional ByVal c As Long = 1) As Long
'MSVBVM60
Private Declare Sub GetMem4 Lib "MSVBVM60" (ByVal lPtr As Long, ByRef ret As Long)
'USER32
Private Declare Function MessageBoxW Lib "USER32" (ByVal hWnd As Long, ByVal lpText As Long, ByVal lpCaption As Long, ByVal wType As Long) As Long
 
Private Sub Form_Load()
    Dim cadena      As String
    Dim ptr1        As Long
    Dim ptr2        As Long
 
    cadena = "karcrack"
 
    ptr1 = StrPtr(cadena)
    'StrPtr__
    Call GetMem4(VarPtr__(cadena) + 8, ptr2)
 
    MsgBox (ptr1 = ptr2)
 
    Call MessageBoxW(0, ptr2, 0, 0)
    Call MessageBoxW(0, ptr1, 0, 0)
End Sub

STPRT Get the BSTR Address(where the string is stored) so is simple get it

Readmemory(Varptr + 8) = BSTR

enjoy