Is there any way to know how many bytes I allocated? Example:

Code:
char *mystring = (char *) malloc ( 100 * sizeof(char));
mystring = "1234512345";
Is there any way to get the "100" somehow?

sizeof(mystring) returns 4
strlen(mystring) returns the total number of bytes up to a null termination (10)

How do I get "100"?