First, the better solution is to add this property (HasChanged) to your control - for VFP code is the same if this property is on your control or on the form, but for your code this will be easy and clear. There is way to do this property on the form, but your ActiveX will be usable only from VFP - it will not work in VB and also the way, which I will show you, will not work in other languages like VC++.

Anyway, the way you can do this: use ParentControls collection. VFP support this collection (but VC++ does not support it). In this collection when your control is on VFP form you can access every control on the form (and also columns in grids etc.). Do loop through this collection until you find the form and change its property.