Your question is little bit confusing , i think you want to get 3 different report on button click according to your combobox selected value .
you can do as follows:
'Inside button click event
dim objrpt As Object
dim val as integer
val= Me.cmbAsst.SelectedValue
If val= 1 Then
objrpt = New report_1
ElseIf val= 2 Then
objrpt = New report_2
ElseIf val= 3 Then
objrpt = New report_3
End If