sampling

[mark]

I need to generate a number of samples in a dataset using the 6 and 7th characters from an alpha series with 60K records. Here is an example data point:

02101OP0004

I've tried tyo sample the set using various combinations of wildcards to not avail - I get "sample has no observations". Here are example sample statements.

if contractum="?????OP????"
if contractnum="*OP*"

Help please!

[EViews Gareth]

if @mid(contractum,6,2) = "OP"

[mark]

thanks