Excel VBA macro. Some cells are automatically filled when a template is used to create a document.

Today, I wrote an Excel macro. When I create an Excel file based on a template, the content of some cells is automatically filled according to the current machine environment.
 

The writing is clumsy, because you are not familiar with VBA and office events, and you are all looking at help. If you can give me some advice, please leave a message.

Private sub workbook_open ()
Dim STR as string
STR = trim (range ("g22"). value)
If STR = "" then
Range ("g22"). value = now
End if
Dim Z as integer
Dim Z2 as integer

If range ("A1"). value = "" then
Z = Day (now) mod 7
Z2 = Day (now) 7
If (z> 0) then
Z2 = Z2 + 1
End if
Range ("A1"). value = "(" & month (now) & ")" & "Week (" & Z2"
End if
End sub