Yes, you can identify a ComboBox by its ValueMamber property:
Dim c As Object
For Each c In Me.Controls
If TypeOf c Is ComboBox Then
If c.valuemember = "<ValueMemberName>" Then
c.Text = "Found It!"
End If
End If
Next
Note: for <ValueMemberName>, substitute the ValueMamber you want to find.
Also, if the comboboxes are in a sub-container on the form - such as a Panel or GroupBox - you will need to use that in place of Me:
For Each c In Panel1.Controls
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