Open a Blob for Write access (create a Blob)                 
function PXBlobOpenWrite
   (RecHandle        : RecordHandle;   { record handle cotaining Blob field }
    FldHandle        : FieldHandle;    { field handle of Blob to create     }
    var BlbHandle    : BlobHandle;     { Blob handle used for writing       }
    Size             : Longint;        { size of Blob to create             }
    SaveCurrent      : Integer): Int;  { save current Blob in field?        }
Errors: PXERR_TYPEMISMATCH       30  Data type mismatch
        PXERR_OUTOFMEM           40  Not enough memory to complete operation
        PXERR_BLOBOPEN           52  Blob already open
        PXERR_BLOBINVSIZE        54  Invalid size for Blob
        PXERR_BLOBMODIFIED       55  Another user modified Blob
        PXERR_INVFIELDHANDLE     75  Invalid field handle
        PXERR_INVRECHANDLE      104  Invalid record handle |