Code:
/*
 * eg4.c
 *
 *  Created on: Aug 23, 2011
 *      Author: UshaC1
 */
/*******************************************************************************
**                      Include Section                                       **
*******************************************************************************/
#include<sys/time.h>
#include<stdio.h>
#include<time.h>
#include<string.h>
#include"stdlib.h"


#define Number_of_Tasks 5  //Number of tasks in a scheduler




/*******************************************************************************
**            F U N C T I O N    D E C L A R A T I O N S(API)                 **
*******************************************************************************/




int nTimeInterval;//Global Timer value

void Task_10();
void Task_20();
void Task_30();
void Task_40();
void Task_50();
void Task_60();
void Task_70();
void Task_80();
void Task_90();



void Task_10()
{
    printf("Task1 at 10ms executing\n");
    printf("Task2 at 10ms executing\n");
}

void Task_20()
{
    printf("Task1 at 20ms executing\n");
    printf("Task2 at 20ms executing\n");
}

void Task_30()
{
    printf("Task1 at 30ms executing\n");
    printf("Task2 at 30ms executing\n");
}

void Task_40()
{
    printf("Task1 at 40ms executing\n");
    printf("Task2 at 40ms executing\n");
}

void Task_50()
{
    printf("Task1 at 50ms executing\n");
    printf("Task2 at 50ms executing\n");
}

void Task_60()
{
    printf("Task1 at 60ms executing\n");
    printf("Task2 at 60ms executing\n");
}

void Task_70()
{
    printf("Task1 at 70ms executing\n");
    printf("Task2 at 70ms executing\n");
}

void Task_80()
{
    printf("Task1 at 80ms executing\n");
    printf("Task2 at 80ms executing\n");
}

void Task_90()
{
    printf("Task1 at 90ms executing\n");
    printf("Task2 at 90ms executing\n");
}

void run_task(struct time *val)
{
    int i,correction;
    float elapsed_time;
    static int j=0;//counter
    j++;
    printf("%d\n",j);

    for(i=0;i<Number_of_Tasks;i++)
    {

        if(val[i].remaining_time == nTimeInterval)
        {
            clock_t start = clock();        //start a clock
            printf(" Execute %s at %d milliseconds \n ",val[i].task,val[i].period);//calling scheduled task here
            Task_[val[i].period]();// here i am calling a function that is giving error

            

            elapsed_time=((double)clock() - start) / CLOCKS_PER_SEC; //Time taken to complete a task

            /* To check whether my task take more time than nTimeInterval */
            if(elapsed_time > nTimeInterval)
            {
                printf("Time elapsed: %f\n",elapsed_time);
                correction=elapsed_time-nTimeInterval;  //correction in time
                nTimeInterval=nTimeInterval+correction; // adding the correction to nTimeIntervals
                printf("%d\n",nTimeInterval);
            }
            val[i].remaining_time = val[i].period;


        }
        else
        {
            val[i].remaining_time -= nTimeInterval;
        }

    }
}

Here is my code ... in function runtask i need to call my function Task_10,Task_20 or anyother according to the variable var.period so how can i call a function using a variable as a function name ??? .. here i have dome something but its giving error please help me in this concern soon.