Summing based on column value

I am trying to total a column, ITQTY#. The thing is, if it's a negative value, they store this negative symbol in another column - ITQOHA.

The below is not compiling, 'The remaining text does not appear to be part of the formula' We have to code so that we don't subtract a negative from a negative which would yield a positive. What is not correct here?

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shared numbervar aaa

if {ICDET1.ITQOHA} = ' ' aaa = aaa - {ICDET1.ITQTY#}

else

aaa = aaa + {ICDET1.ITQTY#}