Skip Multiple Rows when copying formula

PLEASE HELP!!!!!

New to forum - much appreciation in advance.

I have a linked formula tying spreadsheets together. The layout of the second sheet is different than that of the base sheet so I need to formula to skip 3 rows at a time from the base sheet.

Here is the linking formula in column B of the second sheet:
='[Inventory PLUS.xlsx]Sheet1'!A5


In the very next row of the second sheet I need it to pull from 3 rows down from the base sheeet (A8), or more precisely ='[Inventory PLUS.xlsx]Sheet1'!A8

In the next subsequent rows I need the formula to pull from (A11,A14,A17) always adding 3 rows from the base sheet each row moved down on the second sheet.

So, in essence I want my B column to go as followed:
B1 ='[Inventory PLUS.xlsx]Sheet1'!A5
B2 ='[Inventory PLUS.xlsx]Sheet1'!A8
B3 ='[Inventory PLUS.xlsx]Sheet1'!A11
B4 ='[Inventory PLUS.xlsx]Sheet1'!A14

and so on and so fourth, continuing down the sheet as there are a lot of different inventory and I am always adding more parts.

- If you have any input, it would be greatly appreciated.

Being that this is my first post I know I may have to explain better but any info you could send me would be greatly appreciated.