how i can do it ? adding sub-assembly with pro/program

if my choice "1" i want to add only "SECTION_1.ASM"

if my choice "2" i want to add "SECTION_1.ASM"and"SECTION_2.ASM"

if my choice "3" i want to add "SECTION_1.ASM"and"SECTION_2.ASM"and"SECTION_3.ASM"

if my choice "4" i want to add "SECTION_1.ASM"and"SECTION_2.ASM"and"SECTION_3.ASM"and"SECTION_4.ASM"

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INPUT

SECTION_NUMBER NUMBER

"SECTION NUMBER CHOICE ( 1, 2, 3, 4 )"

END INPUT

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where is the problem in my program ?

IF SECTION_NUMBER==1
ADD SUBASSEMBLY SECTION_1
INTERNAL COMPONENT ID 40
END ADD
END IF

IF SECTION_NUMBER==2
ADD SUBASSEMBLY SECTION_1
INTERNAL COMPONENT ID 40
AND
ADD SUBASSEMBLY SECTION_2
INTERNAL COMPONENT ID 41
PARENTS = 40(#5)
END ADD
END IF

IF SECTION_NUMBER==3
ADD SUBASSEMBLY SECTION_1
INTERNAL COMPONENT ID 40
AND
ADD SUBASSEMBLY SECTION_2
INTERNAL COMPONENT ID 41
PARENTS = 40(#5)
AND
ADD SUBASSEMBLY SECTION_3
INTERNAL COMPONENT ID 49
PARENTS = 41(#6)
END ADD
END IF

IF SECTION_NUMBER==4
ADD SUBASSEMBLY SECTION_1
INTERNAL COMPONENT ID 40
AND
ADD SUBASSEMBLY SECTION_2
INTERNAL COMPONENT ID 41
PARENTS = 40(#5)
AND
ADD SUBASSEMBLY SECTION_3
INTERNAL COMPONENT ID 49
PARENTS = 41(#6)
AND
ADD SUBASSEMBLY SECTION_4
INTERNAL COMPONENT ID 54
PARENTS = 49(#7)
END ADD
END IF