how can I modify EI-33 core transformer?

Hello,

I need a transformer that will amplify voltage of my input signal to three times bigger amplitude. I mean I need 1:3 step up transformer. How can I made it by using power supply's EI33 core?

My input signal is 25-45khz, 300V_peak_to_peak, squarewave

Expecting output signal is : 25khz-45khz ,900V_peak_to_peak,squarewave


thanks