timer control on vb 2010 to arduino

hi this is my first post. my friend just bought an arduino duemilanove for my project. im trying to send strings to arduino using vb 2010 application so that i can turn a pin on and off at a given time. this is my code: all settings have been applied ( Dim result As String result = TxtBox1.Text + TxtBox2.Text p.WriteLine(result) ) txtbox1 will send the hour and txtbox2 will send the minutes to the arduino. i would like to store my system's time and the given time to the arduino microcontroller, and if the given time is equal to my system's time then a certain pin would turn off and on. i could try to use the vb application to send the the string at a given time but that would require my pc to be on. i just need to know the code for my arduino sketchbook cause i cant seem to figure it out :(

thx in advance.

How about getting a real-time clock on the Arduino and let it do the whole thing? The Arduino's internal timer isn't particularly accurate, so you'd need to have something running on the PC correcting it quite often in order for it to time anything accurately.

Just out of curiosity, what will be connected to the pin that is turned off and on?

the component that would be connected to the pin is just an LED, but my friend is trying to put something bigger
anyways now i know that storing time in the arduino board is inaccurate, ill just use the vb app that i will create
to send the signal to the arduino at any given time.

thx.