problem with checkBox

[alwayslags]

hi ppl,
ive got new problem today. i have checked checkbox. i want to do something like this: after unchecking this checkbox i want to textbox change status to readonly

ive got something like this

private: System::Void checkBox1_CheckedChanged(System::Object^ sender, System::EventArgs^ e) {
if (this->checkBox1->Checked == false)
{this->textBox7->ReadOnly = true;}}

well, program runs, checkbox is checked, but after unchecking textbox doesnt change its status to readonly. i want to make so after unchecking no1 could change data in textbox7