message box should display in their own tab page of tab control

Question

hi every one ,
i have tab control in windows from
tab control,consist of multiple tab page namely:tabpage1,tabpage2,tabpage3,tabpage4

tabpage1 consist of  two textbox and submit button
tabpage1:txtusername,txtpassword,btnsubmit.

similarly
tabpage2  consist of web browser control which connects to yahoo page

when iam specifying WRONG username, password and submitting -it will verify login credentials with the database.
at the same time iam clicking the tabpage2 which will display yahoo page.
In the background login verification is going on ,once it complete it will display message box saying that 'invalid login credentials'. but currently iam in tabpage2 so this message box should not appear when iam in tabpage2 or any other page other than tabpage1.
so to overcome  i written a line sof code before the messagebox of login.

codsearch.TabControl2.SelectTab(0)

codsearch.TabControl2.TabPages(0).Focus()

formname=codsearch
tabcontrol name=tabcontrol2

messagebox.show('invalid login credentials') 

since  iam  doing this login verification using a subroutine of another class.
which is written out of the form (eg: class)

so any idea to overcome this.

warm regards 
arifsharif_2001