"Unsatisfied forward or external Declaration" error message in Delphi

"Unsatisfied forward or external Declaration" error message in Delphi

Unit unit1;
/// By clin003 at 20070423 from: http://blog.csdn.net/clin003 //////////////////////////
Interface

Uses
Tlhelp32, shellapi ,;

Type
Tform1 = Class (tform)
Procedure formcreate (Sender: tobject );
Function shellrun (Spath: string; sparam: String = ''): Cardinal; {if this is the case, an error is returned here.
[Error] unit1.pas (29): unsatisfied forward or external Declaration: 'tform1. shellrun'

}
Private
{Private Declarations}
Public
{Public declarations}
End;

VaR
Form1: tform1;

Implementation

Function shellrun (Spath: string; sparam: String = ''): Cardinal;
Begin
..
End;
End.

/// By clin003 at 20070423 from: http://blog.csdn.net/clin003 //////////////////////////
{The reason for this is that a method is defined but not implemented (there are doubts here)
In fact, this function can be implemented in this way:
Function tform1.shellrun (Spath: string; sparam: String = ''): Cardinal;
Begin
..
End;

}