Excel on Iphone , using formula

[Kiwi den]

I would like to use a spreadsheet on iphone, using formulas so i can type into cell (sheet1, A1) a number. ( this number will relate to a list on sheet2 A1 - C200, namely column A) what i would like is for cell (sheet 1 B1) to show the number on sheet2 relating to the the list from sheet2 column C) my problem is i would like to update the number in cell (sheet 1 B1) and for this to update on sheet2
hope this makes sence, i was going to use a vlookup, in cell sheet 1 B1, but that will result in deleting the formula

thanks in advance