It is imposible if convert this formula to Function
 Function BecomeWord(Byval Tek as range) as string
' i want change A1 with Tex 
BecomeWord=PROPER(IF(A1=0;"nol";IF(A1<0;"minus ";"")&SUBSTITUTE(TRIM(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(SUBSTITUTE(IF(--MID(TEXT(ABS(A1);"000000000000000");1;3)=0;"";MID(TEXT(ABS(A1);"000000000000000");1;1)&" ratus "&MID(TEXT(ABS(A1);"000000000000000");2;1)&" puluh "&MID(TEXT(ABS(A1);"000000000000000");3;1)&" trilyun ")&IF(--MID(TEXT(ABS(A1);"000000000000000");4;3)=0;"";MID(TEXT(ABS(A1);"000000000000000");4;1)&" ratus "&MID(TEXT(ABS(A1);"000000000000000");5;1)&" puluh "&MID(TEXT(ABS(A1);"000000000000000");6;1)&" milyar ")&IF(--MID(TEXT(ABS(A1);"000000000000000");7;3)=0;"";MID(TEXT(ABS(A1);"000000000000000");7;1)&" ratus "&MID(TEXT(ABS(A1);"000000000000000");8;1)&" puluh "&MID(TEXT(ABS(A1);"000000000000000");9;1)&" juta ")&IF(--MID(TEXT(ABS(A1);"000000000000000");10;3)=0;"";IF(--MID(TEXT(ABS(A1);"000000000000000");10;3)=1;"*";MID(TEXT(ABS(A1);"000000000000000");10;1)&" ratus "&MID(TEXT(ABS(A1);"000000000000000");11;1)&" puluh ")&MID(TEXT(ABS(A1);"000000000000000");12;1)&" ribu ")&IF(--MID(TEXT(ABS(A1);"000000000000000");13;3)=0;"";MID(TEXT(ABS(A1);"000000000000000");13;1)&" ratus "&MID(TEXT(ABS(A1);"000000000000000");14;1)&" puluh "&MID(TEXT(ABS(A1);"000000000000000");15;1));1;"satu");2;"dua");3;"tiga");4;"empat");5;"lima");6;"enam");7;"tujuh");8;"delapan");9;"sembilan");"0 ratus";"");"0 puluh";"");"satu puluh 0";"sepuluh");"satu puluh satu";"sebelas");"satu puluh dua";"duabelas");"satu puluh tiga";"tigabelas");"satu puluh empat";"empatbelas");"satu puluh lima";"limabelas");"satu puluh enam";"enambelas");"satu puluh tujuh";"tujuhbelas");"satu puluh delapan";"delapanbelas");"satu puluh sembilan";"sembilanbelas");"satu ratus";"seratus");"*satu ribu";"seribu");0;""));"  ";" ")))&" Rupiah"
End Function