Referencing column values in a grid is a little different than you may have seen before. When using a standard list you can reference the value of a column using an XSLT variable of the same name ($COLUMNNAME). This is not possible with the grid so it is necessary to access a column with the following XPath expression:
../lxml:column\[@name='COLUMNAME'\]
This is not necessary for referencing the current column (i.e. the column containing the weblet). In this case you can use a single period (.). If you know the position of the column you want to reference, you can use an Xpath expression like this:
../lxml:column\[2\]
This is handy for large lists as it is much faster but it may cause problems if you change the order of the columns in your list.