Hi ,
Source of problem is every time you click on button there is new instance of a form is created which is different from other.
Now there is two way to solve this problem.
Declare then base or main form as a mdi form and check your code is
If Me.MdiChildren.Length > 0 Then
For Each frmChild As Form In Me.MdiChildren
Next
Else
End If
Another way to maintain a static Dictionary of object of form and form name as key. On button click check is object is already exists the activate it or create a new instance of form.