Confusion about Scope of workbooks and worksheets

I fell unsure about understanding the Scope of workbooks and worksheets

Context of question:
Within one module associated with a single workbook
Within a single subroutine
If I open an existing workbook and existing worksheet within the open workbook
assigning a variable to each of the above objects

then make a function call within the above single subroutine
I am assuming the code inside the function call
Has no idea which workbook or worksheet is open

Hence I assume I must pass the variable name for the workbook and
worksheet as parameters to the function call and use them to extract
data from the worksheet

Question:
Do I understand the scope of workbooks and worksheets within a single subroutine?

First....Thank you so much for responding. I am very grateful.

ok....so this is what I put together in my mind from reading your message to me:

* there is a hierarchy of objects: workbook includes worksheets which includes range
* initially range must define the worksheet it is a part of AND
* initiallu a worksheet must define a workbook in which it was defined

Interestingly, each object knows who its parent is and who its children are! I have imagined that the parent only knew its children but the children did not know who its parents were!!!
and so whenever any of the above objects are used, the parents (workbook -> worksheet) are known

now....while the default active workbook may be know....and the default active worksheet may be known....i am opening myself up to problems if multiple workbooks are open.

Hence I feel I want to define the workbook or worksheet i will be working on instead of just using "activeWorkbook or Thisworkbook.

So...do i do that by passing the worksheet name to the function or subroutine...and just continue using that worksheet name inside of the function or subroutine? If so, i would love to pass just the pointer to that worksheet adn not the whole object. how do i do that?

Secondarily, if i am worried that the worksheet might have an identical worksheet in another workbook, perhaps I should pass the workbook variable (or pointer) as well?

what do you do? i do not have a feel for how specific I should be

When there are multiple workbooks open (or multiple worksheets that might be active) it is common to make the desired workbook and/or worksheet active and then take an action, as opposed to "staying where you are" (in terms of which workbook or worksheet is active) and specifying which workbook or worksheet to act upon by prefixing. E.g. you might go

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as opposed to

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It's a theoretical tradeoff. On the down side, Activating first and not prefixing can
- have a small extra amount of CPU processing (which might build up to a significant amount depending on the scenario)
- maybe be distracting since the display changes (perhaps even annoyingly flicker)
- It is not as explicit as specifying the object.

However if those are not of concern (which is often the case) then not having to prefix operations might make the code easier to follow. By going wbSales.Activate you might avoid typing
wbSales.
9 times in the next several lines of code. One benefit of the resulting "compactness" might be that some lines of code don't extend off the right side of the screen, or require underscore line continuation, in order to see all code without scrolling. You or another code maintainer may also be able to more quickly mentally process what code is doing when removing the "distraction" of the prefixes. However, it's still a tradeoff. Explicitly saying wbSales. would in some cases actually make the code easier to read and maintain.

If performance and readability/maintainability are not a big factor, I often just Activate the workbook or worksheet of concern first just because I personally find it easier to mentally follow along. At least it's much easier for me during initial code development to have the object active so I can quickly toggle alt-F11 to see what's happening, even if later on I add in prefixes and remove Activate lines.

Now having said all that I still may have to do the prefix
ActiveSheet.
despite all my "lazy" efforts to avoid having to prefix operations. Again, it's a tradeoff such that different projects may call for .Activate and others might not. I'm just pointing out that there are two ways to go.