Not sure if it is the best way or recommend way, but I found a better way to handle this. As I had to pass a VBA form as an Object argument to the ActiveX dll in any case I added a Property Get/Let to the form to set the value indicating the interrupt. When this propery is changed in the .xla it will be picked up by the dll and it saves running a function in the .xla. I wasn't aware that

What would be the simplest way to interrupt a running procedure in a VB6 ActiveX dll? I call this dll from Excel and I would like to interrupt the procedure if the spacebar is hit. There is no problem to do this when all the code is in VBA and I can simply change a global variable when a control keyboard event is fired when that control has the focus, in this case a treeview control, but