getElementByid("myObhectId") return null???

[qtptester]

Thank you for your answer Ravi
but probably i did not explain fully the problem :

myObhectId is not an object that i have in myobject repository
now i want check if getElementById("myObhectId") returns me an object present in the page.

wrote my function as you did

Code:

set input=Browser("title:=.*").page("title:=.*").Object.getElementByid("myObjectId")

If  isobject(input) Then
    input.Click
End If

if i set an object id of an webutton present in my page it works correctly
but i need to check if getElementByid returns me no objects :

now if i write a wrong object id it still tries to do input.click
i don t know why isobject is not working how it was expected
but probably i don t know how getElementByid works

thank you