Sum expression with multiplication

I have already defined 5 different parameter for a category.
and created Point Set ( PTAX1 ).
in Point Set's (PTAX1) attribute 'PDIS' I want to mention two mathematical calculation.
A) Sum > PARAM5 & 0.810 TIMES PARAM 4
What is expression for it in PDIS attribute ?

I have already defined 5 different parameter for a category.
and created Point Set ( PTAX1 ).
in Point Set's (PTAX1) attribute 'PDIS' I want to mention two mathematical calculation.
A) Sum > PARAM5 & 0.810 TIMES PARAM 4
What is expression for it in PDIS attribute ?