How to offset importrange() within an arrayformula() - google-sheets

Question

I have two Google Sheets (separate documents) that contain information, let's call them Master & Source. Within Source I have an undefined range of cells that are in sorted order by date that I need to display within Master. Master is intended to have links to all the various Source sheets, in normal operation, I'll have multiple of these, so I can view all of the quick information about all of the Source sheets displayed conveniently in Master. Master contains a date range that starts before and ends after the date range from within Source (to accommodate other date ranges from other Source sheets).
My goal is to create a single cell formula that can be copied and pasted for each Source that I need to view in my Master that would fill the cells in columns before and after the date range from Source with the string "No Class" and all the cells that match the date range from Source would simply be a copy/reference to the matching cell from Source. This is the formula I came up with:
=ARRAYFORMULA(if({A1:Z1;A1:Z1;A1:Z1;A1:Z1;A1:Z1}<importrange(Link!B4,"Source!A1"),"No Class",if({A1:Z1;A1:Z1;A1:Z1;A1:Z1;A1:Z1}>Link!N4,"No Class",importrange(Link!B4,"Source!A1:Z99"))))
Link!N4 = Start Date
Link!B4 = hyperlink to the google sheet `Source`
Amazingly, it works quite well, except for one major drawback: the array of values from importrange are relative to the cell that the formula is in - aka, the range from Source starts at Master!A1 rather than starting at the first column that has the same date as Source!A1.
This is a screenshot of the result of my formula in Master. *EDIT: No Class has conditional formatting to make the font color match the fill, so you can't see it in this screenshot, but they are the dark grey cells.
And another screenshot, this time of the Source I'm trying to view.
I realize this approach might not be the only way (or might not work at all) but each time I try something else it always comes down to the same problem: how do I dynamically start the importrange at the first column that matches the date from Source using a formula that is in the first cell?

Answer 1

I found an acceptable workaround. This is by no means a solution to the problem of trying to offset data within an array, but it allows me to get what I needed to be done. This code needs to be filled using the fill handle (blue square on the bottom right of the selected cell). I'm adding this here in the event someone gets in a similar situation and needs an alternative way to look at the problem.
=iferror(if(importrange(Link!$B4,"Source!A1")>A2,{"No Class";"No Class";"No Class";"No Class";"No Class"},if(importrange(Link!$B4,address(1,COLUMN(A3)-match(importrange(Link!$B4,"Source!A1"),$A2:$Z2,0),4,TRUE,"Source"))=A2,importrange(Link!$B4,address(2,COLUMN(A3)-match(importrange(Link!$B4,"Source!A1"),$A2:$Z2,0),4,TRUE,"Source")&":"&address(5,COLUMN(A3)-match(importrange(Link!$B4,"Source!A1"),$A2:$Z2,0),4,TRUE)),"No Class")),{"No Class";"No Class";"No Class";"No Class";"No Class"})
A2 is the date of the column in master I'm trying to import into, it changes as your drag the fill handle.
A3 is the cell that the formula is currently in
This works by first checking iferror (but I'll come back to that).
Then, if the date in the same column as the formula is less than the start date "No Class" fills the column (hides dates prior to start date)
ELSE If the date in the same column as the formula is the SAME as the date in the column of the Source (offset by the number of columns away from the start date) then fill the column with the corresponding column from Source (aka, this fills one column at a time, rather than importing the entire range at once).
(Back to iferror) An error is returned for any columns that come after the end date - so iferror fills those columns with "No Class"