Updates the current record in a table                     
function PXRecUpdate
   (TblHandle        : TableHandle;           { table to update record into }
    RecHandle        : RecordHandle):Integer; { changed record to post      }
Errors: PXERR_RECLOCKED        9  Record is locked
        PXERR_TABLEWRITEPRO   22  Table is write protected
        PXERR_OUTOFDISK       41  Not enough disk space to complete operation
        PXERR_RECDELETED      50  Another user deleted record
        PXERR_INVTABLEHANDLE  76  Invalid table handle
        PXERR_KEYVIOL         97  Key violation
        PXERR_INVRECHANDLE   104  Invalid record handle
        PXERR_TABLEEMPTY     105  Operation on empty table
        PXERR_TABLELOCKED    119  Table is locked
        PXERR_SXCANTUPDATE   136  Cant update Heap open on Secondary index |