I do it something like this. I'm not moving back to the previous Z position, but you can see how to do it.
Also, I don't see the purpose of this line, and it appears to be missing a ).
Complete=Question ("Change to tool number" & tool
Try this. I actually store the tool change position in variables, as I use M6 End to retrieve the position and move there.
Code "G53 G0 Z " & TCZ
Code "G53 G0 X" & TCX & "Y" & TCY
Code "G0 X" & GetVar(1) & " Y" & GetVar(2) ' Move to Previous XY Position prior to M6 being called