IAP Command execution

Hi,

I need to erase a flash page using IAP commands.
i am doing the following

         IAP.cmd    = 59;
         IAP.par[0] = start_addr;
         IAP.par[1] = end_addr;
         IAP.par[2] = clk;   // 20 MHz
         IAP_Entry (&IAP.cmd, &IAP.stat);

During execution, code is waiting in IAP_Entry to finish the entire operation. It is coming to next line only after completing the IPA Entry execution. This situation causes me to wait there based on the entire erase operation to be finished.

What i expect, it should initiate flash operation and come out of that line and perform other operations. Upon completion, in interrupt handler i can check IAP.stat

The main thing, while debugging, even i am trying to erase more number of pages, it is waiting to entire erase to finish.