What is the difference between "Allah is the One Whose help is sought" (Allah al-Musta'an) and "God willing" (In sha' Allah), and how is each used in the appropriate situation?

"Allah al-Musta'an" (Allah is the one whose help is sought) means seeking help from Allah alone when facing a difficult or perplexing matter. An example of this is the saying of Jacob, peace be upon him, when his sons accused him of lying: "So patience is most fitting. Perhaps Allah will bring them to me all together. Indeed, He is the All-Knowing, the All-Wise." As for "Insha'Allah" (if Allah wills), it means making the occurrence of a future event conditional upon the will of Allah. An example of this is the saying of the Prophet, peace and blessings be upon him, to Itban ibn Malik: "I will do so, if Allah wills."