Can you clarify the situation?  Are you the missionary?  If so are you being paid?  If you are being paid, are you an Employee, or are you an Independent Contractor?  Is your assignment there for less than one year, or is it longer than that?

In your previous post, you said you were on that mission for 18 months.  If that is the case, and if you were paid, there is *NOT* a deduction at all.

No, we were not paid at all for our missionary service.  We paid our own way.  We were gone for 18 months. We paid a monthly fee for our apartment and bought all of our own food.  We paid a rental fee for our truck but did not pay for insurance or fuel

So I am assuming we can take the deduction?

I assume you are referring to a Charitable Deduction?

Yes, you can deduct your ACTUAL expenses, but you can't use the Per Diem amounts.

You can NOT use the standard Lodging amounts; you can only use your actual cost for Lodging.  As for meals, I have never read anything that allows the meal Per Diem for charitable work.  Assuming that no provision exists for that, only your actual expenses can be used as a charitable deduction.