Display Array in listbox

ok well i'm having issues sending a char array to a listbox. To do a little explanation on the code itself... The point of this part is to take a hexidecimal string and convert it to a alphabetical string (this part works and has been tested in a console application). I then have a vShowText function that i used to add items into my listbox. It has worked thus far and i have even added char arrays to the listbox using it. In this particular case i can't seem to make the char array show up into the listbox, it just inserts a line of D like characters. This is sorta difficult to explain so i hope i'm doing a good enough job of it. I will post code to help explain more below.

here is my vShowText function that is being used to insert text into the listbox.

Code:

 void vShowText(HWND        hChildHandle, char *szText)
{
        int Line;
        
        // add string to the listbox
        SendMessage(hChildHandle,LB_ADDSTRING,0,(LPARAM)szText);
        
        // determine number of items in listbox
        Line = SendMessage(hChildHandle,LB_GETCOUNT,0,0);
        
        // flag last item as the selected item, to scroll listbox down
        SendMessage(hChildHandle,LB_SETCURSEL,Line-1,0);
        
        // unflag all items to eliminate negative highlite
        SendMessage(hChildHandle,LB_SETCURSEL,-1,0);
}

below is where my problem is. This is the actual code to change the hex string into a alphabetical one. When the loop is done going through the hex string, ptrBuffer is reset to point to the first element in the char buffer[100] array. Then vShowText is called to display the contents of the buffer array into the listbox. I have also tried to just do vShowText(hlistbox, buffer). Both of these methods does the same thing and inserts a line of D like characters into the listbox... so it looks something like this DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD. Only they aren't actual D's.

also i am able to just make a char array and then later call vShowText with the array as a parameter and it displays in the listbox fine. Example is below.

Code:

//create a char array
char myArray[100] = "Hello World!";

//later in the program
vShowText(hlistbox, myArray);


the actual code snipplet:
 case MENU_FILE_TRANS:
{
        char *ptrBuffer = &buffer[0];

        for (int i = 0; i < RecvBytes; i+=2)
        {
                int firstvalue = RecvData[i] - '0';
                int secondvalue;
                //if RecvData[i+1] is a letter convert it to integer, otherwise use it.
                        switch(RecvData[i+1])
                        {
                        case 'A':
                        {
                                secondvalue = 10;
                 
                        }break;
                        case 'B':
                        {
                                secondvalue = 11;
                 
                        }break;
                        case 'C':
                        {
                                secondvalue = 12;
                 
                        }break;
                        case 'D':
                        {
                                secondvalue = 13;
                 
                        }break;
                        case 'E':
                        {
                                secondvalue = 14;
                 
                        }break;
                        case 'F':
                        {
                                secondvalue = 15;
                 
                        }break;
                        default:
                                secondvalue = RecvData[i+1] - '0';
                        break;
                }
         
         
                //convert the two values into decimal form
                newval =  16 * firstvalue + secondvalue;
         
                //change newval into a character
                *ptrBuffer = char(newval);

                //SendMessage(hlistbox,LB_ADDSTRING,0,(LPARAM)ptrBuffer);
                ptrBuffer++;

                //vShowText(hlistbox, ptrBuffer);
        }

        ptrBuffer = &buffer[0];


        vShowText(hlistbox, ptrBuffer);
        

}break;