Subtract constant to all element of array with assembly sse without intrinsics

I have an array of number from 0-255. I want to calculate 255 - elem for each element in the array with inline assembly in C using SSE instructions.

this is my code:

   #include <stdio.h>
    
    int main(){
       __declspec(align(16)) float a[5] = {250, 18, 48, 16, 15};
       __declspec(align(16)) float constant = 255;
      
       _asm{
          movups xmm0, [a]
    
       }
       return 0;
    }

how can I do that ?

actually I know I can do this:

    int main(){
        const array_number = 5;
        __declspec(align(16)) float ff = 4;
       __declspec(align(16)) float a[5] = {250, 18, 48, 16, 15};
       __declspec(align(16)) float b[5] = {255,255,255,255,255};
       __declspec(align(16)) float res[5];
      
       _asm{
          mov ecx, array_number
          movups xmm0, [a]
          movups xmm1, [b]
          subps xmm1, xmm0
          movups [res], xmm1
       }
       return 0;
    }

but if array a size grows I hove to increase numbers in array b.