=IF(LEN(SUBSTITUTE(A2," ",""))>=5,LEFT(SUBSTITUTE(A2," ",""),LEN(SUBSTITUTE(A2," ",""))-3) & " " & RIGHT(SUBSTITUTE(A2," ",""),3),A2)
This will format anything greater than 4 characters and leave the others as it finds them. You can, of course, change that behaviour.
Regards
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