GNU make - how to concatenate targets within one command

Hi all
    I'm looking for a feature or technique in GNU make - I'm not sure
what it might be called, and it might be achievable only with other
commands.

Basically, I want to concatenate a series of targets in the parameters
of a rule command. As a f'rinstance: If I have a set of .A files, and
a command AtoB which generates .B files, such that

AtoB 1.A    # creates 1.B
AtoB 2.A    # creates 2.B

and
AtoB 1.A 2.A 3.A 4.A    # creates 1.B, 2.B, 3.B and 4.B

My question is, how can I specify a rule so that *all* of the
changed .A files are invoked on the AtoB command line - ie if 1.A, 2.A
and 3.A are changed, I want make to invoke

AtoB 1.A 2.A 3.A 4.A

rather than

AtoB 1.A
AtoB 2.A
AtoB 3.A


Thanks for your thoughts.

    Jon N