I keep thinking there must be a function that allows an address within a cell to be used as a variable within another cell address. For the types of sheets I’m creating it would make my life so much easier.
For the purposes of example, the function I seek is hypothetically called “THING” below:
Sheet1 Daily Menus
MONDAY MENU
Items: Helper Column Nutritional Data Results
A B C
1 =Sheet2!A35 =THING(A1,row=35) =INDIRECT("Sheet3!G"&B1) =Sheet3!G35
2 =Sheet2!A247 =THING(A2,row=247) =INDIRECT("Sheet3!G"&B2) =Sheet3!G247
3 =Sheet2!A989 =THING(A3,row=989) =INDIRECT("Sheet3!G"&B3) =Sheet3!G989
TUESDAY MENU
101 =Sheet2!A613 =THING(A101,row=613) =INDIRECT("Sheet3!G"&B101) =Sheet3!G613
The bottom line is:
In a complex spreadsheet (10 pages, each with hundreds of rows and columns), I want to manipulate the addresses by altering only the data in column A on page 1.
This would also allow me to easily copy column B down for hundreds of rows. The type of function in column B may also be required in columns C, D, E… for dozens or hundreds of columns.
Right now I’m typing in each needed address manually, or a very long function using the address. If anything changes in column A then I have to go back and retype these long functions… and often I find that I’ve made a typo with all that typing…
You seem to have as your starting point formula =Sheet2!A35
in cell A1.
What you have to do is:

Get the formula as a string.
For this you can use either XL4 macros, VBA, orFormulaText
(in Excel 2013 or later), see this. 
Extract the row number from the string.
For this you an use VBA (very easy), or a formula to find the rightmost letter/$
and keep the substring to its right. 
Use the previous answer, as you already incorporated in your question.
Answer to the first version of the question
I will split the formula you are looking for in two steps.
In cell B1 you can enter ="Sheet2!"&"X"&TEXT(A1,"0")
.
This will produce the result Sheet2!X25
.
Then in cell C1 you can enter =INDIRECT(B1)
.
This will bring into cell C1 the contents of cell Sheet2!X25
.
Notes:

You can copy the formula downwards as you need.

When copying into other columns, take care of relative/absolute indexing.

You could use a single formula (no helper column) in B1:
=INDIRECT("Sheet2!"&"X"&TEXT(A1,"0"))
. 
Both
Sheet2
and (column)X
could be replaced by suitable formulas if you want them not be hardcoded. 
Formula in B1 can almost certainly be replaced by
="Sheet2!"&"X"&A1
.
NB: A long time time ago, under circumstances I do not recall now, I found I needed to useTEXT
; YMMV.
Tags: excelexcel, function, sed