How to put a condition on formula

I am making a general calculation to get the line total. this is shipped qty * price.

But, we only want to include when there is a field = 'CRP' or 'TRP'.

This is in a linked table, ICPRT1. IARC11. If i put this on the record select, I get no records. So can I put it in the formula itself?

{OEHIS1.OUNTU$}*{OEHIS1.OUSHP#}