Hi Eric .. one more question.. what the difference if I use below code:

private myobj as object

private sub Form_load()
set myobj=createobject("mydll.class1")
end sub

private sub test()
myobj.run = true
myobj.var1=450
myobj.formula=2
myobj.constant=10
msgbox myobj.result
end sub

private sub Form_unload(cancel as integer)
set myobj=nothing
end sub

and what is your suggestion?

thanks and have a nice day

Regards
Winan