Dear,
If you want to do this having data in 5 different fields then you will need to have 5 fields of type CHAR in your data source and get them populated from your string field.
What is your rule to split? Do you have any delimiter in your string based on which you want to split OR do you want split in sequence like first 60 characters in first field then from 61 to 120 characters in second field and so on.
You could write a logic using following syntax in customer exit (Master data) to split if you want to split based on delimiter value.
SPLIT "STRNG_FIELD" AT "DELIMITER (value of your delimiter like "|" OR ";") INTO FIELD1 FIELD2 FIELD3 FIELD4 FIELD5.
If you want to split in straight sequence then use following syntax.
Move STRNG_FIELD+0(60) to FIELD1.
Move STRNG_FIELD+61(120) to FIELD2.
Move STRNG_FIELD+121(180) to FIELD3.
Move STRNG_FIELD+181(240) to FIELD4.
Move STRNG_FIELD+241(300) to FIELD5.
Take help of ABAPer in your team.
Thanks & Regards,
M