Shell Programming and Scripting

Hi all,

Let's say I have a script calling for the two variables PA_VALUE and PB_VALUE.

Code:

for pa in PA_VALUE 
blah blah
do
for pb in PB_VALUE
blah blah
do

I have a text file with two columns of values for PA and PB.

Code:

14.5 16.7
7.8 9.5
5.6 3.6
etc etc

I would like to read this text file line by line and replace the PA_VALUE and PB_VALUE with these values. The first row, first column would replace wherever PA_VALUE occurs in the script and replace the value in the first row, second column wherever PB_VALUE occurs. Then it would repeat line by line in the text document. I have thus been unable to achieve this. I am familiar with sed to replace values, but unsure how to link it to read a document line by line and replace in another script. Thanks.