VBScript in VB

I am creating a cool Space fighting game called Stellar Attack Six. In this game the user will be able to script their own weapons using vbscript. For example:

sub initializeShot()
    xSpeed = 20 * cos(AngleOfNearestHeatSource)
    ySpeed = 20 * sin(AngleOfNearestHeatSource)
    HeatGenerated = 50
end sub

sub fireShotInterval()
    xSpeed = xSpeed + cos(AngleOfNearestHeatSource)
    ySpeed = ySpeed + sin(AngleOfNearestHeatSource)
end sub

sub impact(objectNumber as long)
    DammageRadius = (100 - fule)/10
    Dammage = 100 - fule
end sub

Ok, thats the general idea. But how do I take the written script and execute it within my program? Do I need some kind of control, or do I need to call an API? And is it possible for the scripter to do anything really sneaky, such as sctipting a virus to download off the internet? If so is there any way I can prevent this?