Hi

I don't know about callback, but I found this once regarding pointer, and did not make search on it

The pointer is simply a memory address (integer) for a variable or object

Try this, and let me know if that works with you.

Declare INTEGER VarPtr IN "msvbvm50.dll" As "VarStrToPtr" String @var
Declare INTEGER VarPtr IN "msvbvm50.dll" As "VarNumToPtr" Integer @var
Declare INTEGER VarPtr IN "msvbvm50.dll" As "VarObjToPtr" Object @var

cName = "S"
ptr = VarStrToPtr(cName)
? ptr && 57831008

nNum = 1000
ptr = VarNumToPtr(nNum)
? ptr &&  1241216

oObj = createobject("Session")
ptr = VarObjToPtr(oObj)
? ptr