Scroll a multi-line screen with LINE OFFSET

This script uses LINE OFFSET to repeat one screen line five times, so the operator can enter and scroll through several records on the same screen. It handles the up and down arrows and the page up and page down keys.

LN   BTLLINE
SN   BTSLINE
DD   START-LINE(2.0), SCROLL-FLAG(1)
MAINLINE
     OPEN SCREEN BTSLINE
     OPEN LINK BTLLINE
     PRINT SCREEN BTSLINE
     READ BTLLINE USING KEY RANGE FROM FIRST TO LAST
        PROCESSING IS DELETE-RECS
     INPUT SCREEN BTSLINE PRE PROCESS FIELD1, GET-START-LINE
     LET L = 1                          !line number or key to each record
     LET L1 = 0                         !line offset or position for printing
     DO LOOP UNTIL TERM-KEY = 4
        DO GET-DATA
        PRINT SCREEN BTSLINE DATA
           LINE OFFSET L1
        INPUT SCREEN BTSLINE DATA-NAME FIELD2 LINE OFFSET IS L1
           POST PROCESS FIELD2, SCROLL
        IF TERM-KEY <> 4 AND SCROLL-FLAG <> "X" THEN
           ADD BTLLINE USING KEY STR(L:"00000")
              DUPLICATE KEY PROCESS IS DUPE-RECORD
           LET L = L + 1
           DO CLEAR-DATA
           IF L1 < 4 THEN
              LET L1 = L1 + 1
           ELSE
              LET L1 = 0
              LET L = L - 4
              DO INCREMENT-DATA
           ENDIF
        ENDIF
        LET SCROLL-FLAG = ""
     ENDLOOP

SCROLL                                  !what type of scrolling to perform
     IF TERM-KEY <> 0 THEN
        LET SCROLL-FLAG = "X", BTSLINE.FIELD = 99
     ENDIF
     IF TERM-KEY = -4 THEN              !testing for up arrow
        DO CLEAR-DATA
        IF L1 > 0 THEN
           LET L1 = L1 - 1
        ELSE
           IF L > 1 THEN
              LET L = L - 1
              DO INCREMENT-DATA
              LET L = L - 3
              LET L1 = 0
           ENDIF
        ENDIF
        IF L > 1 THEN
           LET L = L - 1
        ENDIF
     ENDIF
     IF TERM-KEY = -3 THEN              !testing for down arrow
        DO CLEAR-DATA
        IF L1 < 4 THEN
           LET L1 = L1 + 1
           LET L = L + 1
        ELSE
           LET L1 = 0
           LET L = L - 3
           DO INCREMENT-DATA
        ENDIF
     ENDIF
     IF TERM-KEY = -17 THEN             !testing for page up
        PRINT SCREEN BTSLINE DATA CLEAR
        IF L1 > 0 THEN
           LET N = L1
           DO CLEAR-DATA
           LET L1 = 0
           IF L > 1 THEN
              LET L = L - N
           ENDIF
        ELSE
           LET L1 = 0
           IF L > 5 THEN
              LET L = L - 5
              DO INCREMENT-DATA
           ELSE
              LET L = 1
              DO LOOP UNTIL L = 5
                 DO GET-DATA
                 DO CLEAR-DATA
                 LET L = L + 1
                 LET L1 = L1 + 1
              ENDLOOP
           ENDIF
        ENDIF
     ENDIF
     IF TERM-KEY = -16 THEN             !testing for page down
        IF L1 >= 0 THEN
           LET L1 = 0
           DO INCREMENT-DATA
        ENDIF
     ENDIF

CLEAR-DATA                              !clears data from specific fields
     PRINT SCREEN BTSLINE CLEAR DATA-NAME LIST FIELD3, FIELD4, FIELD5
        LINE OFFSET L1

GET-DATA                                          !setting your key equal to
     LET BTLLINE = "", FIELD1 = STR(L:"00000")    !a specific line#,reading
     READ BTLLINE USING KEY FIELD1                !the file and printing the
     PRINT SCREEN BTSLINE DATA-NAME LIST FIELD1, FIELD2       !entire record
        LINE OFFSET L1

INCREMENT-DATA                           !increments the line number and line
     DO GET-DATA                         !offset in order to get the corect
     DO CLEAR-DATA                       !record on the correct line.
     DO LOOP UNTIL L1 = 4
        LET L1 = L1 + 1
        LET L = L + 1
        DO GET-DATA
        DO CLEAR-DATA
     ENDLOOP

GET-START-LINE                !sets up for correct line and field positioning
     LET START-LINE = BTSLINE.LINE, BTSLINE.FIELD = 99

DELETE-RECS                             !erase the entire file
     DELETE BTLLINE USING KEY FIELD1

DUPE-RECORD                             !allows you to change data records
     LET A$ = BTLLINE
     CHANGE BTLLINE USING KEY STR(L:"00000")
        PROCESSING IS CHANGE-DATA

CHANGE-DATA                             !performs the change
     LET BTLLINE = A$

ENDSCRIPT                               !end of program

Notes

The script uses screen BTSLINE and link BTLLINE. Each record is keyed by its line number.
When it starts, the script deletes every record in BTLLINE (procedure DELETE-RECS), so try it on a test link.
Press F4 to end input.