The UBA wishes all foreign radio amateurs and their families, who plan to visit our beautiful country, a very pleasant stay. We feel sure you will enjoy this multicultural country, where most people speak at least two, and many 4 or 5 languages. Communicating in English will be no problem!

Belgium complies with the CEPT Recommendation TR61-01 and 02 and if your country does as well, the licensing procedure will be quite easy:

If you have a radio amateur license with the CEPT mention (CEPT TR61-01), and if your stay is not longer than 3 months you can operate a radio amateur station using your own call preceded "ON/" (ON slash your call). Example: if your call is W1XYZ you will use the call ON/W1XYZ.
If you plan to stay longer than 3 months and if you hold a HAREC operator certificate (CEPT TR61-02), you can apply for a Belgian Callsign, which probably will be a ON9-call. Contact BIPT/IBPT, the Belgian regulatory body regarding radio licenses.
If your PTT administration didn't sign the CEPT agreements, you can ask for a special guest license. Send an inquiry letter with a photocopy of your license to BIPT/IBPT. In any case you should include a photocopy of your licence together with the study program relating to the radio amateur examination in your country. The whole procedure may take quite a while and no guarantee of success.