guys, please help my excel for my estimation.

i want to add value in same cell across multiple workbooks.

example:
vduct 1F.xls sheet1 A1
vduct 2F.xls sheet1 A1

down to

vduct 35F.xls sheet1 A1

there is 35 workbooks in all.
i want to add cell A1 in from vduct1F.xls - sheet1 to vduct 35F.xls - sheet2
im adding it one by one by adding each cell in each workbook. but after the 6th formula input, it says "too long formula".

hope someone will help me..
thanks in advance..