Split up the string with whole word

Friends,

I have a string with 150 charcters.

I want to split it up in 50-50-50 charcaters but the requirement is the word should not be broken.

So the 150 characters field can be adjusted.

and if there is no space in 150 characters then it should split exactly 50-50-50.

Is there any function module available for that?

Regards,

RH