Maybe you can split score to 2 (or more) number attributes, so say you have scoreLow to store the decimals and digits up to 999999999.99 (something in the allowed range, and scoreHi to get highest values. You can check overflow when increasing score, and have scoreLow += remainder( scoreLow / 1000000000) and overflow units added to scoreHi, the può togheter the two in a text like scoreTxt = toText(scoreHi)+toText(scoreLow).
Sould be feasible with stencyl blocks.