Yeah.  Add the SYSModules table and join the Source field of your table (PLPostedSupplierTrans ?)  to the SYSModuleID field. Then add either the Name or the ShortName from SYSModules to your report.

Ok thanks, I've had quick look but I can only get Purchase ledger fields by the looks of it. Might be me i'm not too experienced at this! Thanks. 

OK. Select Report -> Joins from the menu. Above the toolbox at the left-hand side is a 'Find' box. Type SYSModules into that box and click the little green arrow next to it. The contents of the toolbox will narrow down to the Sage 200 Accounts data source; you can expand this and you should find only the SYSModules table in there. Drag the SYSModules table onto the main design surface where the other tables are.  Then click the 'use raw text editor' button in the lower left. The last few lines in there will probably begin with 'STATIC JOIN...... ' 

Add this line directly above the first of those 'STATIC JOIN' lines:

INNER JOIN [SYSModules] ON PLPostedSupplierTrans.Source = SYSModules.SYSModuleID

Then click OK. The SYSModules table will now be available in the list of variables and you can use the Name/Short Name fields in the detail section of your report.

OK. Select Report -> Joins from the menu. Above the toolbox at the left-hand side is a 'Find' box. Type SYSModules into that box and click the little green arrow next to it. The contents of the toolbox will narrow down to the Sage 200 Accounts data source; you can expand this and you should find only the SYSModules table in there. Drag the SYSModules table onto the main design surface where the other tables are.  Then click the 'use raw text editor' button in the lower left. The last few lines in there will probably begin with 'STATIC JOIN...... ' 

Add this line directly above the first of those 'STATIC JOIN' lines:

INNER JOIN [SYSModules] ON PLPostedSupplierTrans.Source = SYSModules.SYSModuleID

Then click OK. The SYSModules table will now be available in the list of variables and you can use the Name/Short Name fields in the detail section of your report.