lily,
Are you trying to split up some exciting data or are you wanting to force the split upon entry?

Is the end result to be spread over say A1, B1, C1.
Bear in mind that A cannot contain the original long string and then the first 30 characters by using formulas. You can however use formulas to split A out into B,C & D
Are you ok using vba or a user defined function?
Is this a one off conversion?

Note also that splitting by character length albeit to the nearest space character will not otherwise split the address into 'logical' readable chunks.

Eg Flat 12, Block B Centenary Tower, Sometown Someplace

wouldsplit...

Flat 12, Block B Centenary - Tower, Sometown Someplace