Help with fields

Hi all,

I was looking for combining fields
I will combine AcDiesel with AEC project number
I don't no of this is possible

I wish from the projectnumber the first two characters and the rest
Something like V2A001 must converted to V2 and the rest A001

%<\AecPr "ProjectNumber">% is the field

I tried something like
%<\AcDiesel $(substr,$(eval,%<\AcVar Filename \f "%fn7">%), 1, 2)>%

But it don't work

Help being appreciated

Regards Harrie