How to send data to a serial port only after getting an acknowledgement in VB.Net

Hey TJ's,
             Need some help from you guys ..Could anyone suggest how do I perform the following task.
I need to send multiple instructions to a controller through a serial port ... So it works something like this.
I read one by one all instructions stored and then send them only after receiving an acknowledgement from the controller say "*" ...However the first instruction in the buffer doesn't need to receive an acknowledgement ............ i know its some simple thing but please guys could you help me out .....I hope you guys understood what i am trying to say .. please do comment on this post and help me out ..... Hoping for the answer as soon as possible