Code:
#define public RequiredSpace "1000"
#define MbToBytes(str *Value) \
Local[1] = MbToBytes((Value)), \
Local[1]
[Setup]
AppName=111
AppVersion=0.0
AppPublisher=bbbbb
DefaultDirName={autopf}\111
ExtraDiskSpaceRequired={#MbToBytes(RequiredSpace)}
[_Code]
function MbToBytes(Value: Integer): Integer;
begin
Result := (Value * (1024 * 1024));
end;