First time in Pascal

This is the first time that I write code in BP7. Could anybody tell me if
this sounds right.
The code referenced various units. I am sure that they are OK. What I am
trying to do is to generate a numbering sequence and place it in the
short_note field. This is declared as short_note: String [7]

procedure BeforeSave(pParamForInvc: ptParamForInvc); export;
{************************************************************************}
{DESC: Called just before the Document is written to disk.               }
{Sigo: Will open a file on the C:\ (root) (c:\terminv.txt)               }
{to take the last invoice number used and save it to Short_Note          }
{************************************************************************}
var
  mycBuff: string[5];
  mycShortNote: string[5];
  myHandle1: shortint;
  myInvcnum:longint;
  myFileNam: string[15];
begin
  myFileNam:= 'C:\TERMINV.TXT';
  myHandle1:= FileOpen(MyFileNam);
  FileSeek(myHandle,-5,2)
  FileRead(myHandle,MycBuff,5);
  Val(MycBuff, MyInvcnum, code);
  MyInvcnum:= MyInvcnum+1;
  Str(MyInvcnum,myShortNote);
  pParamForInvc^.pInvoice.^.Header_Data.Short_Note:= myShort_Note;
  Fileclose(Myhandle1)
end;

Thanks in advance