How do i combine multiple conditions / rules

[mross]

I am extracting a description for my mail merge ..
{ if {mergefield description} = "instalment interest''Instalment cost" "{description")

this works as expected but I want to add, if mergefield description = Power, then exclude , as I don't want to see that line at all. I don't know how to exclude, I've tried skipif, but that has not worked. All i can get is a line, with no data on it . Please help

[macropod]

{IF{MERGEFIELD description}= "Power" "" {IF{MERGEFIELD description}= "instalment interest" "Instalment cost" {MERGEFIELD description}}}