I'm just starting out.

1. How can I set a text box to accept only integers?
2. I have created a "Submit" button on a form which posts data
entered in the form onto a spreadsheet. If all textboxes are not
filled in (with numbers > 0), I would like to put up a message box
complaining that this is the case and refusing to proceed until all
data is filled in. There are 36 text boxes (conveniently labeled
textbox1 - textbox36), and I suppose I could put in something like If
textbox1 >0 and textbox2>0.......... I'm not really sure how to do
this, but there has to be a better way, no?
3. I want to do a populate a textbox (37) with a value obtained in a
vlookup. I can do this, but I want to lookup in a database which is
occasionally augmented, so I don't want to hardwire the range
selection. I know how to get the number of the last row, and the last
column doesn't change, so I imagine there's a way to put the variable
representing the last row in the vlookup formula, but I can't figure
it out.