How to modify the symbolic variable text in a drawing using protoolkit?

Oh, I solved it! Here is my code. 

void modifySymInstence(ProDtlsyminst &sym_inst, ProDtlvartext &var_text)
{
	ProError status;
	ProDtlsyminstdata data;
	ProDtlvartext *text;
	ProLine prompt, prompt_target, value;
	int size;
	status = ProDtlsyminstDataGet(&sym_inst, PRODISPMODE_SYMBOLIC, &data);
	status = ProDtlsyminstdataVartextsCollect(data, &text);
	ProArraySizeGet(text, &size);
	for (int i = 0; i < size; i++)
	{
		status = ProDtlvartextDataGet(text[i], prompt, value);
		status = ProDtlvartextDataGet(var_text, prompt_target, value);
		if (wcharToString(prompt) != wcharToString(prompt_target))
			continue;
		text[i] = var_text;//It solved my problem
	}

	status = ProDtlsyminstdataVartextsSet(data, text);
	status = ProDtlsyminstErase(&sym_inst);
	status = ProDtlsyminstModify(&sym_inst, data);
	status = ProDtlsyminstShow(&sym_inst);
	ProDtlvartextFree(*text);
}