You have to check misspellings

Above is original code, there is a misspelling in the function name
"function SaySomthing" should be "function SaySomething"

AT

oO = createobject("MyClass")

oO.SaySomething()

oO.cMessage = "Pong!"
oO.SaySomething()

return

define class MyClass as Custom

cMessage = "Ping!"

function SaySomthing
  wait window (this.cMessage)
return

enddefine