how to say "if not"....

[Joey]

is there a quick and easy phrase in japanese that means "if not" for example:
いそがしくなかったら、XXXXXXXXXXXXしてください。
"If not" (instead of 忙しかったら）.....
thanks in advance!

[Psy]

You just wrote it, mate. Though I daresay this isn't the most common way to phrase such a thing. It might be more common to ask something more like "if you have time" l もし時間があれば・・・

[Joey]

alright, thanks Psy-san