Content in “picaxe serial communications”

I need an idea to solve a small problem. When I communicate with the picaxe using sertxd and serrxd, I can send data from the picaxe to the computer with sertxd and the computer will put the data in a buffer, so I can read them, when I have the time. The problem is, that there apparently isn't such a buffer on the picaxe, so if I want to send data to the picaxe, I have to wait until the picaxe is at the serrxd command, before I send.