Setting up variables for the userForm on Workbook_Open() - ERROR 91

Dear colleagues,
Since my last EXCEL VBA application passed two years and now I started the whole new project. I did already a lot of works and now I wanted to set some variables to be set on excel opening. So this is what I did: the userform is called "CACalc" and at the beginning I'm declaring variables:

Option Explicit
Public wb As Workbook
Public taryfy_sheet As Worksheet
(... more ...)

I would like to have those two variables already set when the excel file is opened. I created then this method in the "ThisWorkbook" object:

Private Sub Workbook_Open()
CACalc.wb = (ActiveWorkbook.Path & "\" & ActiveWorkbook.Name)      ' <-- error 91
CACalc.taryfy_sheet = wb.Worksheets("Tariffs")

CACalc.Show
End Sub

When I run the project I receive the "Error 91, Object Variable or with block not set " in the shown line of above code. This can be solved if I change the variable "wb" type to "String", but I'd like to have it as "Workbook". What I'm missing? The goal is to use those two variables in the userForm code to get the data from the excel sheet:

Dim Number as Integer
(...)
' Number = Workbooks(wb).Worksheets(taryfy_sheet).Range("H28")    ' <--- this caused the ERROR 9, when 'wb' and 'taryfy_sheet' were string with correct values
Number = taryfy_sheet.Range("H28")     '<--- this is the goal of the subject

And by the way: I get the error 9 in above code although the variables were correct . When I enter the object "Workbook(wb)." after pressing CTRL + SPACE I get the list of possible methods and object to select. However whatever I select "Worksheets" or "Sheets" followed by the index (e.g. Sheets(2) ) after the next '.' I don't have a list with other methods and objects. I was expecting "Range" or "Cell" available but I get nothing. I will appreciate you help.

Best regards,
Michal

Thank you very much for your advice. Of course it works, unfortunately partially.

set CACalc.wb = thisWorkbook    <---- This is OK
set CACalc.taryfy_sheet = wb.Worksheets("Tariffs")   <-- generated error: '424' Object required.

I tried to set the object type as "Worksheets" or "Sheets" but this generated the same error message.

Regards,
Michal

Hi Norie,
The solution you proponed worked. Thank you.
I am setting those variables because I remember problems when I was creating an application 2 years ago. The app worked fine until the next excel document was opened and "active". If I switched with my mouse and activated the "main" excel document, that I didn't have any problems, but when I saw the user form, but some other excel document was in the background there were some errors shown - I was doing also some other works an work and sometimes it required some other excel document to be opened (casually) - 10 times app worked without a glitch and suddenly the errors about missing variables, object required and so on. Then (suddenly) it works again and few hours later the same. Two days until I connected those two facts :-) This is why now I am setting those two variables at the beginning, so even if I have more excel documents opened my app will always work correctly.