How to get the size of a pointer for LPSTR?

I would like to get the size of the whole data in lpSTR in the following
after I insert some 'data' into data.

int *data = new int[100];
LPSTR lpStr;
lpStr = (LPSTR) data; //I am trying to convert the 'int'data to 'LPSTR'data.
// is this correct ?
//insert data
delete [] data;

What is the command for obtaining the size of lpStr ?
Please help me!
I would like to appreciate your help in advance.