Changing vth for 74HC14(4v)

[Lids]

Hi there, 

I am wondering if there is a way to change vhigh of the 74HC14 (hex inverting shcmitt) for a two-tone buzzer circuit I am making. I require a 3V input but cannot seem to change from the default values (either 2 or 4). I have tried inserting a virtual connection with VCC and changing that to 3v but I am still getting 4v p-p. 

Also, is there any way of changing vt and vh like you can in ltspice? I have attached my circuit for viewing. 

Any help would be awesome

Cheers

Lids

[Lids]

Or does anyone know any other forums that are a bit more active and helpful than this one that I could ask my question to?