Hi Rodney - welcome to the forum.
SendKeys works just fine - but remember that sendKeys targets the application that has focus. If you're running sendKeys from the VB editor in Mach or from a button, then Mach has the focus... so it's sending keystrokes to itself.
Enter this into the VB editor in Mach.
sleep 10000
sendKeys("abc")
before you run it, open a copy of notepad. Then run the script - you then have 10 seconds to give notepad focus. Personally I dislike SendKeys, it can have nasty effects if you focus the wrong app.
As far as accessing a DLL from VB script - just do it as you would from any implementation of VB - use createObject.
Ian