Yes, your margin value changes daily. Since your pledged securities are valued at the previous day's closing price, the margin you get can go up or down as stock prices move. If the value of your pledged securities drops significantly, you may receive a margin call. This means that you'll need to either pledge more securities, sell your holdings or add cash to your account to make up for the shortfall. 

You can see the exact margin available against each of your pledged securities directly on the ArihantPlus app, so there are no surprises.