excel formula between external worksheets

[joelg77]

I am creating a total xl worksheet linked to 5 different xl worsheets. I can happily create the formula to give me the right answer but need this same formula to be replicated over 200 others lines. When dragging down using the cross in the corner of the cell, it copies it exactly the same rather than adding the next row number to the new cell. I don't fancy manually changing the numbers over the 200 lines, 5 x a formula. Please help

[#2]

Please specify the formula you are copying down.

[#3]

@Twifoo 

='[points and costing - flat 1.xlsx]materials'!$I$4+'[points and costing - flat 2.xlsx]materials'!$I$4+'[points and costing - flat 3.xlsx]materials'!$I$4+'[points and costing - flat 4.xlsx]materials'!$I$4+'[points and costing - flat 5.xlsx]materials'!$I$4 

when i drag down on the total page i need the numeral in the !$I$4 parts to change  

[#4]

Remove the dollar sign before the number 4 to make the reference relative.

[#5]

thank you very much sir. Saved me a lot of time on a Sunday evening

[#6]

You’re very much welcome.