Okay I solved it. First of all thank you very much for your help and your quick answers Dave!
Since I use the forum regularly to solve problems, I wanted to provide a solution myself. So for everyone who has this or a similar problem.
I tried to commuinicated with the Varioport through the serial/com port. I could measure lets call it a blip at the start and the end of the experiment, but wasn´t able to send any signals with Inquisit myself.
What you have to do to communicate with Varioport, if it is hooked to the serial/com port, is to initialise or deactivate the port. Inquisit simply can´t do that on command, but does it very shortly at the start or end of the experiment. Hence the measured blip.
If you have to use the com/serial port its easy to do in matlab just initialse the port and fopen/fclose it.
In Inquisit you´ll have to use the LTP port. Here a snippet of my code
<port ltpmax>
/ port = LPT1
/ subport = data
/ items = ("11111111")
</port>
<port ltphalf>
/ port = LPT1
/ subport = data
/ items = ("10000000")
</port>
<port ltpoff>
/ port = LPT1
/ subport = data
/ items = ("00000001")
</port>
**This is taken from one of the Stroops provided by Millisecond
<trial tg_neu_gel>
/ pretrialpause = 0
/ validkeys = ("f", "v", " ", "j", "n")
/ correctresponse = ("v")
/ stimulustimes = [1= ltpmax, square_gelbg; 2=g_neu] **First signal with max output at the first stimulus (255)
/ posttrialpause = 40
/ responsemessage = (" ", ltphalf, 1) **Now, without the " " empty answer, it would not let me send the ltphalf signal with 1ms duration. (Flying blind here. Can´t do a test run right now, at least Inquisit doesn´t complain about this.
So this may be wrong. ). But still on response a second signal half as strong as the first one (128).
/ ontrialend = [ltpoff] **Keep this in mind
http://www.millisecond.com/support/docs/v5/html/howto/howtocontroltiming.htm . The signal will be send after the posttrailpause. Last signal at the end of the trial (1).
</trial>
Hope this helps someone.