No problem. To edit/create macros that run when you open a tab, do the following:
1) Right-click on the tab and select View Code...
2) This will show the vba window and any macro assigned to that sheet
3) If the macro is already there it will be shown.
4) If you need to add a macro to a sheet so that it runs whenever the sheet is opened, you need to change the two dropdown boxes (General to Worksheet), (Declarations to Activate).
5) Edit the Private Sub Worksheet_Activate() code to include your macro code.
6) That code will now run whenever the sheet is activated.
If you need any more advice, just let me know.