invalid left-hand side in assignment when changing value of cell

Not entirely sure which variable you are referring too. Theres three variables in this problem. The ArtNumChkT is a table variable. The counter variable, which is an integer. It's simply there to help me go trough the table. Lastly the ChkTrimArtNum is a parameter in the script function. I haven't seen any options to specify that the table or the parameter should be a string so I assume TestComplete figures that out itself. 

In the Debug mode I can see that it takes and uses the value in the parameter so that should be fine. However the aqString object might not work if it does not consider it a string.

So I made some progress, or so i think. 

function TrimArtNum (ChkArtNumTrim){
  Log.Message(ChkArtNumTrim); 
  var counter = Project.Variables.Counter;
  var ArtNum = Project.Variables.ArtNumChkT.Item(0, counter);
  ArtNum = aqConvert.VarToStr(ChkArtNumTrim);
  ArtNum = aqString.Remove(ChkArtNumTrim,0,15);
  Log.Message("test " + ArtNum);
  
  Project.Variables.ArtNumChkT.$set(" Project.Variables.ArtNumChkT", 0, 0, ArtNum);
  
}

 I added a second variable (ArtNum). Artnum goes trough the code properly. What still remains though is saving this value to the cell. I figured this is where i'd use the set method I've been reading about. However, now I get another error: 

Error: The object does not support this property or method. It referring to the %set line.