Cheap radio master-slave

Hello,

I am building a master - slave combination to read out some Arduino's.
The master collect all the information from the slaves.
I have this radio's:
http://www.benl.ebay.be/itm/251446898432

I would like to use Virtual Wire for these but I don't know how I can poll the slaves?
These radio's are only one way I think so does somebody know a 'system' to poll the slaves, maybey without a polling command from the master but with something else. I don't know...

Cheers,
Dylan

Hard to poll one way radios.
Really need transceivers, such as:

Otherwise, have the slaves send "in the blind" at some time interval, with a good enough message structure the master can determine that a complete, non-corrupted message has been received. Maybe the manchester encoding in virtual wire does that already; if so, include an identifier for the sender, and maybe add a check sum to the end just in case.
Add all the bytes in the message, say you had
0x03 address
0xf2 data byte 1
0xa4 data byte 2
0x22 data byte 3
0xb7 data byte 4
= 0x0272, so 0x72 is the total
the check sum could be the inverse of 72: 0b01110010 >> 0b10001101 = 0x8E
So the sum of the first 5 plus the last one: 0x72 + 0x8e = 0x00
So message sent is then:
0x03 0xf2 0xa4 0x22 0xb7 0x8e
Receiver checks that 6 bytes came in, adds them all, and confirms the result = 0
Then process the 4 bytes for slave #3.

I bought also some NRF24L01+'s like you set. The 433Mhz transmitter and receiver will be used for something else.

Thanks!

Cheers,
Dylan