NOTICE TO PROCEED

We have a cost plus award fee contract that cover 6 different areas of the Installation, the Contractor is requesting to buy a piece of supply for one of the Divisions. Funds were included already in the contract when the option year was exercised. To approve this request, can I used a notice to proceed, in which I expecify the funds not to exceed amount and the APC code to be charge or do I need to do it using a SF-30? Please advice.