Clarion 5.5PE legacy application import procedure

Hi!

I have a TPS data file that stores signals received from a modem.
Most of the time the previous record contains the Caller ID information and
its protocol would be type 4.
If the signal is a type P, I would like to look at the previous record see
if it it is a type 4 then make sure the account number matches the current
record in memory. If both conditions are true assign the date and time from
this previous record to the record in memory and then save the record in
memory as the last record in the file.

I wondering if by reading the previous record if my current variables in
memory ((SLRW:Protocol, etc) will be overwritten without me assigning new
values to them. I am not getting any compile errors. In otherwords, I only
want to replace the values of SLRW:DATE & SLRW:Time if there are values
found in the previous record.

Are there any errors in my logic?

Thank you in advance.

Chuck

Part of a case statement

   SLRW:PROTOCOL = CLIP(SUB(RxString,1,1))  !Assignment
   SLRW:RECEIVER = CLIP(SUB(RxString,2,2))  !Assignment
   SLRW:LINE_NO  = CLIP(SUB(RxString,4,1))  !Assignment
   IF CLIP(SLRW:PROTOCOL) = 'P'
                       SLRW:FIELD_4 = CLIP(SUB(RxString,6,11))
                       PREVIOUS(SLRMessages)                !new code **
read previous record **
                       Loc:Protocol = SLRW:Protocol
                       Loc:ReceiverAccountNumber =
LEFT(CLIP(SUB(SLRW:FIELD_4,3,4)))
                       Loc:DateReceived = SLRW:Date
                       Loc:TimeReceived = SLRW:Time
                       IF SLRW:PROTOCOL = '4' AND
LEFT(CLIP(SUB(SLRW:FIELD_4,3,4))) = Loc:ReceiverAccountNumber
                            SLRW:TIME = Loc:DateReceived
                            SLRW:DATE = Loc:TimeReceived
                              ELSE
                                SLRW:TIME  = CLOCK()
                                SLRW:TIME  = INT(SLRW:TIME / 6000) * 6000 +
1
                                SLRW:DATE = TODAY()
                       END!IF                               !end of new code
                       SLRW:FIELD_6   = '-'
                       SLRW:FIELD_7   =
CLIP(SUB(RxString,17,Len(RxString)-17)) !Assignment
                       SLRW:Imported   = 1
                       ELSIF CLIP(SLRW:PROTOCOL) = 'S' !not supported
protocol
                        CYCLE
                          ELSE              !if non digital format
                          SLRW:FIELD_4  = CLIP(SUB(RxString,5,16))
!Assignment
                          SLRW:TIME     =
DEFORMAT(CLIP(SUB(RxString,21,5)),@T1) !Assignment
                          SLRW:FIELD_6  = CLIP(SUB(RxString,26,1))
!Assignment
                          SLRW:DATE     =
DEFORMAT(CLIP(SUB(RxString,27,8)),@D5) !Assignment
                          SLRW:TERMNTR  = CLIP(SUB(RxString,35,1))
!Assignment
                          SLRW:Imported = 1
                   END!IF
                   ADD(SLRMessages)                !
                   ADD(SLRQueue)                   !!Add message to the
queue
                   Display(?List)                  !!
  END!IF